Tanking in general is a miserable, miserable experience. I've been tanking as a power tech in this game since release (played a level 50 mercenary through beta), and it really is awful.
I've been quite vocal about it too and nobody that matters seems to care.
Trash is a giant nightmare and I honestly think it was made the way it is just to troll the very few people who actually want to tank. Charging into a group of elites only to get knocked back for 6 seconds CONSECUTIVELY is just ridiculous. Trying to pick up a group of NPCs (who stun, knockback, or knockdown on contact) with one of two crappy AOE damage abilities that can only be used 4 times before overheating makes me want to curb stomp an infant.
On any normal boss fight, I pop DPS cooldowns in between my normal rotation, as well as DPS relics and DPS adrenals and players in my raid will still pull aggro. And it's not like I'm some level 50, fresh off of Illum, I tanked from about level 13 through 50 and even before that, I tanked in World of Warcraft for about two years of my seven year "career" in that game.
The fact of the matter is, 50% threat modifier is a joke when you're tanking for players who actually know how to play their characters efficiently.
I would suggest going DPS. Play a spec that won't make you want to quit the game.