Well, it's supposed to be. It's very powerful, but also very rare, unless your mission maker is... game balance challenged. It's not supposed to replace the T100 as a frontline main battle tank, but rather, think of a T-140 platoon as a sort of "boss fight" at the end of a coop campaign, or as an incredibly expensive vehicle that mostly just speeds up the last half hour of a PvP game that's about to end. It's also used as a soft time limit for a mission ("complete this objective in under xx minutes, or reinforcements will arrive and make it much harder"), an out-of-bounds mechanic ("you can go anywhere in this mission, but every were but the objective, here and the main routes in between have T-140 sections), etc...

So yeah, it's very overpowered. That's the point. But if you see more than one K variant, and/or more than one T-140 platoon in a mission, your Zeus is either a very poor gamemaster, or trusts you enough to succeed with the tools you have. Or, in the case of PvP, the local rich Navid clan can afford to just shell out for several each game without repercussions, in which case I urge you to go to the gamemode's designer and inquire about their narcotic chemical intake.