I don't think that it is op.
Karotte> Air is fast and have no problmes to move to a target.
Not the Krow.
> (shields are senseless against air, be cause they can easyaly walk under, and to kill other units you can fly to your enemy and qiuckly back.
Have you ever seen how fast 2 Chainsaws kill a Krow?
And how many time you need for repair a Krow?
That each long range ground unit is very effective against them?
Chainsaw has a bigger range then the most Arti units.
You can build a big Bertha if you want a really invulnerable unit.
It is true and good that ground units hit the Krow hard.
But because the combination of speed / range and the time it needs to kill even a small bulk of units it is under powered.
If we don't give it a time-limited speed booster it can't handle even a bulk of snipers.
( have someone tried to stun a Krow with Rakeeters or spys :D )
An arty cannon should only do damage like a minelayer vehicle, but it should enable it to hit penes and kill short range stuff like a flak over time.
Or do you really expect that one flak protect you against a 5k metal unit?