It is apparent to all that stamina builds are lacking. Here are some thoughts that I have had in regards to balancing them.
1) How come all class abilities are based on magicka? This has made no sense to me. I play a nightblade so I will start there.
There is two approaches that can be taken with this. Either the entire tree can be stamina or magicka based (Assassination stamina, Shadow 50% stamina and 50% magicka, Siphon magicka) or each skill could be a variation (Assassin's blade stamina, Teleport Magicka).
Keeping each tree as an entire same cost base would be simpler and many classes seem to have a clear flavor in these regards. It should be noted though that not every class would or should work this way. Sorcerers for example don't really have anything that jumps out as stamina based. I think that we all think of the sorcerer as a purely magicka based class, and nightblades make the perfect hybrid class. Dragonknights probably should have a heavy stamina emphasis, perhaps only having one magicka line, or perhaps two 50/50 lines. Templars on the other hand should be heavily magicka based with only one stamina line or two 50/50 lines.
When I talk about 50/50 skill trees or lines, I mean that if an ability has a cost of 350 it would cost 175 magicka and 175 stamina.
In most cases most classes should be optimized to use both magicka and stamina. The Sorcerer is the only one I can think of currently that does not fit that mold. It just makes sense that if you are doing actions and attacks that involve weapon swings and attacks that some stamina be used as a basis for that attack, such as assassins blade. If ZOS was to go with individual adjustments it could get really interesting. Perhaps the base skill is stamina based and one morph changes it into a magicka based skill.
In conclusion of this first suggestion I believe it is clearly the issue that stamina is used for the rather generic, weapon based skill lines. Since all class abilities are magicka based, everyone wants to be magicka based. You become a nightblade because you want to use nightblade skills. The generic weapon lines could be somewhat described as a "base warrior" class. Make class skills use stamina and stamina builds become more relevant.
2) If the above suggestion seems to be too much there is another option. Introduce magicka versions of sprint (teleport), dodge (blur), block (force shield), and interrupt (force spike). By allowing stamina builds to use magicka for their survival and utility resource pool they can then devote 100% of their stamina resource pool to damage, just like the current magicka builds can. Even if the above suggestion is taken, this should still be done.
If ESO truly wants to break the cookie cutter syndrome of MMO games, then it needs to provide an array of similar options for skills and powers that all do not a close approximation, but exactly the same numbers as each other. Then it will not matter if you use magicka or stamina, you will just bee choosing to produce the same numbers in a different way. Then it just becomes artistic style.