Consume plasma has been the strongest stolen skill since 2012.
Lets look at the stolen skills:
Mace crack- melee, removed with stunbreak
Essence sap - needs target, can be dodged (though 2nd strongest stolen skill)
Whirling axe - melee, long channel that you can get damaged in.
Throw gunk - small radius, weak effect.
Healing seed - stationary, has cooldown.
Blinding tuft - short duration, s/d thief doesn't benefit much from stealth, harder to get because you need to steal on a thief, only benefits the opener/escape not mid combat.
Ice shard - melee, can be cleansed
Skull fear - long channel, can be dodged.
Stolen skills are either attacks that need to hit a target (and either melee or slow cast), or defense with limited useability and cooldown like healing seed. This means that the thief must take risks and be think about it in order to get value out of the 2nd stolen still from improv, by going in melee range or doing a slow channel for instance. With plasma the thief just steals, jumps behind LoS, and uses it twice. Because it doesn't need to hit a target, doesn't need LoS, doesn't need melee, doesn't need to be spread out because it stacks so well. It scales too much with improv + sleight of hand + swindler's equilibrium.
Doesn't matter the situation, thieves will steal on the mesmer to get the boons, any opportunity cost is lost because it is always worth it. Playing a squishier build (e.g. power chrono) feels like playing "the floor is lava" vs top thief (try facing sind, pain, etc). Or like playing as "a gas station".
Consume plasma has recently garnered attention due to boonbeast, and surprise it is broken there as well. Just Imagine if there was a utility that gave all boons in the game, on a <20 second cooldown.
Even thematically, why does mesmer stolen skill give boons while guardian's gives daze and engi's gives etheral field? That seems backwards.
Now I am aware some will take this an april fools joke because it contains the words "thief", "broken", and "nerf". This thread is about one skill, consume plasma, not about the entire class.
(Btw, do you like the clickbait title?)