It does desperately need multiple buffs and a cost decrease.
The FlakHT doesn't need direct buffs per se.
However, it does suffer immensely from having its projectiles collide with whatever little tree/wall/little obstacle happens to be on the way.
Sure, Most non-Centaur tanks also suffer from the safe fate. However, with other tanks, you can simply relocate to a better vantage point and fire away. However, the FlakHT has to stop and setup. That makes it very awkward to use. It would be nice if they could make the FlakHT more consistent (e.g., more accurate, but less suppression-per-volley).
With the upcoming balance patch, I don't see the point of ever buying a FlakHT, when I can buy the cheapest MG in the game.
(With every other faction in the game, I would definitely buy the AA HT for its AA capabilities. However, for OKW, that point is moot, since they get free-popcap AA with their T4).