I find stupid Spells and Talents designs quiet interesting, but I started playing WoW sort of recently, in Cata so missed out on a lot of fun stuff, like stories of overpowered Deathknights who had three specs which were all DPS and Tank at the same time in Wrath, Warlocks who only cast Shadow Bolt in TBC, and Hunters that only cast Steady Shot in TBC and would like to hear more in-depth explanation of those and others.
Let me first show Examples of what I believe to be very stupid Spells or Talents so you get the idea. For my first choice, we need to look back no further than the Present by taking a glance at Hunter Pets. The Ability "Combat Experience" increases Damage by 50%, but all Hunter Pets Specialisations have that, so so there is absolutely no difference in Damage increased.
In the next Example we have Cataclysm Talents. They start out with really weak with almost no difference, like the choice between some Spells Critical Chance increase by 4% or other spells Casttime increase by 0,1% which is meaningless. And near the Finish you have the "choice" between your 1 Ultimate Talent like Ardent Defender which reduces all Damage taken and lets you survive a Killing Blow OR go back in the talent tree and pick a weak talent like a slight Reduction on a Stun-Cooldown. Better give the Riddler a call about this Brain-teaser which Talent to pick.
Now it's your turn, do you remember stupid Spells, Abilities, or Talents designs? Every Expansion's Talent Trees are provided here for your convenience for easier remembering.
Vanilla Talent Calculator:
Burning Crusade Talent Calculator:
Wrath of the Lich King Talent Calculator:
Cataclysm Talent Calculator:
Pandaland Talent Calculator: