I'm grinding on Tat to get mine from Level 7 to 8.
I encourage anyone who doesn't have them unlocked yet to do so. The unlock is a huge step forward in the game. The stat improvements after that are incremental.
I only use them in Wars these days, but the improved stats are worth it to me. It's the ability to run further and / or take out more than one shield, if the shield generators are close enough, that I like.
Reducing the frag pool is also a factor. The more things you max out, the more frags you get of the units you actually want, as DS said.
HQ Prestige - Sons of Death & Midnight Mob
You must do what you think is right, of course.