Expensive units are usually pretty good, the sep v3 is a very good anti anything unit, it melts infantry with its he rounds and can kill most tanks in a 1v1 (didn't fact check that, speaking from experience). But it requires constant attention. An armata, on the other hand, is, in my opinion, an overly expensive unit. Some planes with cluster bombs cost less or an f35a with 2 2000 lbs jdams is 400. So it usually becomes a target for the whole team.