First I feel obliged to say something I hate saying to anyone about a game they were once invested in, "Not all games are for everyone." This is a bitter pill and it sucks to say but if you are not having fun and you wanna quit no amount of forum post is going to change that until your feelings change.
With that out of the way, my gut tells me you want to like this game. Most people when they face something they don't like they immediately retreat without a word or second guess, but you decided to come here instead, hoping to find something that might return you to whatever you had before the patch. Well you are in luck.
First, it doesn't sounds like you had a great grasp of the game or its mechanics prior to the patch (console players were at a bit of a disadvantage here as they didn't have long to get a full grasp of the game and mechanics before this major update). So a little background on the basics. It sounds like you are a magic build (unknown class) looking to fill the role of DPS. Before we get into builds, gear and skills, lets talk a little about the game. Many players want progression, but progress in an MMO is often misleading. You could be moving through content but not understand how you got there or what it takes to continue going and it sounds like that is what's happening to you now. You've managed to get to VR5 but have not learnt what it takes to grow your character from there. So to remedy this lets look at where magic damage comes from.
DPS:
Your main components of damage is your resource pool, in this case magic, spell damage, and abilities . You obviously know that having lots of magic means more damage from skills but did you also know that spell damage is determined by the weapon in your hand. Many magic users look to the staff here and in the past have seen lots of damage proc's from the element associated with your staff. This however has been changed in the new patch and elemental proc's are less frequent (which is a considerable hit to DPS). So how do we make up this extra damage. The answer is we increase the base damage of abilities through spell damage. In the past players would look to bolster their magic reserve with the mage mundus stone and in effect they would get a bit of a damage increase as well. While the mage mundus is still a viable option for increasing ones reserve the better DPS option is the rebooted Apprentice stone, which now gives a boost to spell damage. If resource management is not an issue for you take off that mage mundus and go with apprentice, this is a automatic damage increase.
Now that we have you sporting some extra punch for your abilities, lets talk some more about the weapon you are holding. The Destro (or destruction) staff is the DPS weapon of choice in the old patch and is still a very good place to find damage but it is in how we use that damage that determines how you will turn out. One of the most overlooked factors of spell damage is Spell Penetration. How much your attack bypasses the natural amount of resistance your enemy has. In the past enemies had very low resistances and therefore it was easier to kill them. Now almost every enemy in the game is sporting a much thicker coat of resistance and the smart player needs to prioritize spell penetration to get past all that extra resistance. In the old patch the precise trait was coveted as it governed how often you might crit, I would argue that the better trait is now sharpened (nirnhoned if you got it, or you can get a guildie to make it) as this trait directly improves how much resistence you are bypassing to hit an enemies HP. Another good source for spell penetration is the Elfborn Champion point. This passive was bugged prior to this new patch and was not adding to spell penetration properly. Now this passive is fixed and while it may not show up on the character sheet, once you get the right amount of spell penetration, that skill that you thought did little damage will now be wrecking because its not getting blocked or reduced by the improved resistances. This issue then brings me to my next point......
Gear:
I've read that you were using heavy armor which I assume you were doing for the extra damage mitigation while playing solo. Heavy armor is perhaps not the best for a magic build and the "extra survivability" is at best questionable when you consider what your main resource is. Magic builds thrive in light armor, and one great thing about the new patch is light armor has gotten a bit of a boost with the update. Now light armor is half the damage reduction of heavy armor which is up from 25% before the patch. So you first order of business is get some light armor. Not only is light armor a decent source of protection now, it has built in SPELL PENETRATION. Wearing 5 pieces of light armor gives a pretty sizeable amount of spell penetration and when coupled with you greater spell damage and your now properly added spell penetration from CP you should return (if not be doing more damage) to your old destructive ways (see what I did there).
Second, Glyphs (the enchanments on your gear) have been reduced to accommodate the extra VR levels (boo!!!) but here is where you can pick up some extra resource, survivability, or damage. You want to overload on one though. If you need health pick health glyphs, if you need magic....well you get the picture. Try to stay consistent with you glyph choice at least until you reach high levels where you will start to balance out nicely as glyph strength returns.
I'm big on survivability so nothing I will ever advice a player will be glass cannon (although viable). With that stated we have to talk about traits on gear. REINFORCED followed somewhat loosely by IMPENETRABLE are the only ones I would focus on for now. These two are your life savers. Reinforced gives you more resistance, impenetrable reduces the amount of damage you take from enemy crits. Since you will be in light armor reinforced is needed where ever you can get it, but sprinkle in an impenetrable piece or two. You want high resistance to reduce how much damage you are taking.
My last, but most important advice for gear is sets. This one is crucial as the right set has to match how you imagine your character. I love crafted sets. These give you complete control over your character, while found gear is powerful and dungeon gear can prove invaluable in endgame, while leveling in VR you need crafted gear. If you have means, always choose a crafted set. I never pick up gear I intend to use while leveling (only exception is jewelry as there is no crafting for that....yet. There is little reason to use found gear while leveling because you can quickly outgrow it and in the process loose some valuable synergy. At least if you are crafting your gear you are in control of how you look, and how you fight.
Abilities:
I saved abilities for last because without knowing your class any advice I give would be near useless. But I will comment on what I do know. If you are magic user, using a staff, then there is almost a 100% certainty that you are using spells from a destro staff and above all other skills I want to draw attention to a little used mage favorite of mine, WEAKNESS TO ELEMENTS. This gem is a universal debuff and lowers your targets resistance to anything that the game considers a spell. It doesn't cost magic to use and does not have a timer, and for all intents and purposes, it is your new best friend. Cast this skill as often as you can, on pretty much anything that will do you harm. It works amazingly with the added damage, and spell penetration philosophy from earlier. Once morphed it has a small amount of magic return as well so its the ultimate win skill if you ask me.
Now before I go, lets talk briefly about elemental effects. I said earlier that the proc's are less frequent and that is not entirely true. The proc rate has been normalized (which is developer for saying that it will proc regularly within the percentage for abilities). This is a nerf in some instances and a buff in others, what abilities you use will determine which is which for you. As such I look sparingly at elemental damages as the added damage is not always there. Some folks have doubled down on elemental hoping to inflict maximum damage on those proc's but others like myself see that elemental damage/dots are something to accept when you get them but not something to build around (even for the DK, which was at one time a fire god). Now if you must rely on elemental damage look for abilities with high upfront damage, this way if you do get a dot, you can capitalize on both the upfront damage and the dot. This means that lot of those great AoE abilities with low damage and great dots may not be as viable as they once were. Secondary functions will play a big part in what skills make the cut for you, but just to give you an example, I've gone from 5 dots on my DK magic build down to 1.
Closing:
I'm sorry that you feel the game has changed so drastically for you, and judging by the amount of people who share this sentiment who are perhaps not as well versed in this games mechanics, I hope you all can find something from this that has given you a bit of a rough outline to build from. Remember, It has taken the better part of three months to build your character to where it was, rebuilding will not take as long, but it will not be solved in one day either. If you need help try to post specific questions, I mean extremely specific questions. Due to the complex nature of this game and the ever changing landscape it is hard to throw general advice out there without something to back it up and more importantly something to answer directly. With that in mind I apologize if this is a long post, but I read through all the comments and I couldn't help but want to provide as much info as I could to help you get to where you want to go. If you have any specific questions about anything, or need something explained further please ask. And lastly go easy on the forum vets and the L2P response....we see a lot of QQ post about nerfs and imbalance this or broken that and often the answer is that a player needed help understanding a mechanic but didn't properly verbalize that. I wish you the best.
This ws such a great post in a thread I'm sure so few read. With all of the topics on and off the forum about the update I felt this would be of great help. I know it was very helpful for me