This doesn't really fit into the patch discussion, but it fits under the stated goal of narrowing the gap between end-game players and new or even mid-level players. It has been exhaustively pointed out that the proposed changes nerf everyone, rather than raising the floor. I'd like to focus on what I've always believed would be a simple and effective way to raise the floor. There are many combat mechanics that are very different from other games (I've been in MMORPS since Asheron's Call and EverQuest). I was in this game for at least 2 years before I ever heard anyone say "light attacks" much less explained what they were and how to use them. We finally organized DPS, Healer, and Tank training in our trade guild, because it was so opaque. Not every player knows to look for unexplained combat approaches outside the game in video, so let's have them IN THE GAME. Here are some initial thoughts... players may differ on what order they would put these in, but the general idea is that by the time you're level 50 - you've been formally introduced to all the important combat concepts. This would do more to raise the floor than any one other thing.
COMBAT ACADEMY
You would go through combat academy with your first character on an account. There would always be an option to skip it (for players transferring servers) or review any of the lessons at any time.
The initial tutorial when you make a character gives you a few basics: attack with a skill, block, bash, heavy attack. OK. That's probably enough to get you through the first few levels and get used to the game. There's also the suggested skills and attributes help you get as you level up. Let's add some more onto this:
Level 5 Some basics that nobody tells you (other than fairly cryptic comments on the loading screens). Why is there an alchemy skill - to use and make potions, that are essential for buffing your combat. Similarly, making food and drink. Putting enchants on your gear, and what are traits? And hey, not coincidentally, this would be right before 6th level where you can start crafting.
Level 10 Discuss the importance of sets - 5-piece sets, monster sets. Walk them through a typical set, and each of the lines - and how the final line is most important. Explain that you can get sets from overland, dungeons, trials, and crafting. Describe what the stickerbook is, and how they can put pieces in and take them out again, and retrait them.
Level 15 Dedicate this tutorial to light attack weaving. It's time - EARLY so people really know how to use it. Explain cool-down, ultimates, and how potions fit into using the bar. Now introduce the backbar. Explain bar-swapping and animation cancelling, and how to use a combat dummy and combat metrics to evaluate your overall DPS, LAs, which skills are doing the most damage or healing, etc. Don't forget about healers and tanks, and include them in each and every lesson.
Level 20 By this time they've got a fair number of skills, so it is time to talk about the difference between direct damage, single target, DOTs, HOTs, buffs and debuffs. Show examples of each and when you would use them. Explain targeting (e.g., ground-casting, "smart" targetting skills, tab-targeting). Explain which skills typically go on which bar and how to organize them.
Level 25 Explain the different levels of difficulty in the game, e.g., overland, delves, WBs/dolmens, normal/vet/HM dungeons, normal/vet/HM trials, and the basic requirements and rewards for each. Give them a sense of the progression that could be ahead so they are motivated to improve their skills and may have a clue what it means when they see "6-key pledges" in zone chat or Craglorn pugs forming.
Level 30 Explain skill line and racial passives and how they interact with the skills to provide important bonuses (and some penalties). Reiterate that these things also interact with the sets you're using and show examples of the combinations. Get players excited about what they could accomplish with these combinations.
Level 35 They're going to be starting to earn some CPs, so before they get too many, have a tutorial just for this.
Level 40 Start talking about group composition. Healers don't just heal, tanks don't just tank, DPS don't just do damage (unlike some other games). Each has a primary role to play and secondary functions. Explain how these skills and sets can work together to synergistically make a group stronger (compared to a random pug), and how groups can coordinate to avoid duplicating buffs and improve overall damage. Mention player guilds and how they can help you learn and practice these skills in organized groups.
Level 45 Discuss how base-game UI and add-ons can help track and report on combat, alert you to important mechanics, etc. Mention the player-base instruction videos that can help improve combat, learn dungeon and trial mechs, etc. This will all give them a sense of the broad player community that supports this game, which they can tap into.
Level 50 Graduation! Let them review any prior tutorials they aren't clear on, them give them a hard boss to defeat (maybe with a choice between individual and group play). Get some nice reward for completing the entire combat academy - just as they graduate from leveling.