Engineers ruined this game, period.
They still can't get them right 2 years after release.
Pathetic.
It's because they're allergic to removing poorly-performing features from the game. The
only reason that Engineers introduced imbalance into the game in the first place was that they included the special effects on weapons. As soon as people figured out that the new meta was heat, everything became about that. So they tried to rebalance the heat problem (two or three times), by adding more stuff and limiting the effect. Then it became all about the shield-breakers, so they tried introducing more stuff to combat that etc etc...
All they needed to do was remove the special effects, and that would've fixed all the balance issues right away. At least...the balance wouldn't have been any worse than it was before Engineers. The only remaining issue would've been the shield booster problem (ie shield strength increased by an order of magnitude over the possible weapon DPS increases), but that would've easily been fixed by the diminishing-returns shield booster algorithm that they
should have implemented when it was first suggested, instead of putting the shield-breakers in.
The core of the problem is...they don't like fixing stuff, but they
really like piling more stuff on. Throw enough brown stuff at a wall, and eventually...you might have a patch where some of it stuck.