Obviously we can see that the skills and the sets for magicka and stamina are designed by different teams because they are totally different.
I will start that I play DK VR12 S/S 7 light, Magicka furnace set and Akavari Set and I am OP. Most of the people think that DK is very OP and probably it is but let me give you my 2 cents.
I leveled all weapon skills to 50 so I have some knowledge about how they work. I do not have any other class and I played Templar and Sors till lvl 10 in the beta, so some of my information about these classes can be wrong.
Let's start with my proves. I included examples which are available for all classes, not only for certain ones.
Weapon vs Spell critical
Spell critical - if you have 5 pieces of light armors you gain 10 spell critical, inner light 20 spell critical, Twilight's Embrace set 5 spell critical, Willow's Path 3 parts set 5 spell critical, + 7 critical from the weapon trait or 3.5 if we use S/S. Totally 43.5(47) spell critical.
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Weapon critical - if you have 7 pieces of medium armor you gain 21 weapon critical, I do not count Hide of the Werewolf set because it has no VR version, we can use only Night's Silence Set which gives 5 weapon critical, + 7 critical from the weapon trait or 3.5 if we use S/S. Totally 29,5(34) weapon critical.
More critical = more damage and more important faster ultimate gain.
Magicka vs stamina return
Magicka: there is a skill Equilibrium and its morph which can trade health for magicka, there are two sets: Magicka furnace (5 pieces set return 10% of your max magicka with 5 seconds cooldown) - perfect for mele magicka classes, Vestments of the Warlock (3 pieces set composed of accesories) - once per minute, when below 33% Magicka, gain 33% Max Magicka - perfect for casters.
Stamina: none
Magicka vs stamina cost reduce
Magicka - 7 pieces of light armor give 21% magicka reduce of all magicka based skills,
60 magicka reduce from accessories, 3% from Seducer set and 8 % from Worm's Raiment. Totally we can have 32% reduction of magicka based skills + 60 magicka reduction from accessories (there is a cap for this reduction).
Stamina - all weapon skills have passives for reduction with 20% except S/S which has 10% reduction of the cost of the skills and 30% reduction of the block cost (average let's say 20%). These reduction works only for weapon skills not for Alliance war skills or fighter's guild skills. We can have 60 reduction from accesories for stamina skills except block and bash and 84 reduction for block and bash. If we wear 5 pieces of heavy armor we can get 20% block cost reduction No reduction from sets.. Totally we can have 20% reduction for weapon skills + 60 stamina reduction from accessories (there is a cap for this reduction). For block we can have 20% reduction (50% reduction for S/S) + 84 reduction.
Spell penetration vs armor penetration
If you wear 7 pieces of light armor you have 42% spell penetration, which is a passive skill you do not have to waste a precious slot for a skill which debuf your enemy. In the other hand for stamina based skills you need a separate skill to reduce the enemy's armor. If you want to use stamina based AoE skill you should first debuff all your opponents while magicka based AoE directly has the passive bonus.
Other thoughts
Skill as Immovable should not be used unless you wear 5 pieces of heavy armor. Currently is cheaper and safer to use this skill every 8 seconds than breaking the crowd control.
I use my stamina only for blocking and it is so precious so I cannot afford to use any other skills which require stamina usage. Other people use it for sprint or for roll dodge, how do you expect that you will have enough resources to make attacks after that, as we saw that magicka return and reduce is much better that stamina's ones.
As I said I play with 7 light pieces with 900 armor (I do not use any skill to buff it up). Currently if I block a normal attack from a mob and it makes 90 damage, if I play with 2000 armor and I block the same attack I will receive 70 damage. Is it logical to lose all the good passives from the light armor in order to reduce the damage that I receive with 20? I don't think so.
Which weapon skills currently are spamable? Destro and resto staff. Why? Because they do not use the precious stamina and magicka is easily recoverable.
Another stupid thing is ultimate gain while you are not in combat. Several classes have a passive that generates 2 ultimate each time when you use a skill from a given skill line. Also the resto staff has one skill that generate ultimate. We all know what happen when an organized group load their ultimate and rush to the players.
Comparing all these things I firmly believe that two different teams worked on the magicka and stamina based builds. Otherwise it means that the devs just hate all stamina builds. Currently any wise usage of stamina is only for defending skills (block, roll dodge, crowd control break, etc).
Possible solution
Devs please give us the same sets also for stamina, give us a skill where we can trade health to stamina, a passive that reduce the armor, so stamina based AoE are viable and create another statistic which will be used for the defending moves (roll dodge, sprint, crouch, break crowd control) except block.
TL, DR
Magicka based builds are way more OP than stamina based builds. But you probably already knew that.
Because I can!