You are correct - the problem not just in one feature, but in combination of three:
- cloak (no way to spot other than proximity or recon plane AFAIK)
- ability to move while cloaked
- ability to retreat if spotted or caught with pants down
When you play OKW you hate Rak because of how susceptible it is to AoE (tight crew formation) and to small arms fire (short range).
When you play against OKW you hate Rak because reasons stated above.
In my personal opinion there is no reason for Rak to be able to move when cloaked.
OKW mains will come here ask for a buff "to compensate" for removal of this ability.
I bet there will be talk about how Rak unlike other AT guns doesn't provide green cover, but that cover bonus is buggy as hell and works only from certain angles to AT gun. IIRC this behavior was researched by Elchino. So in fact Rak's low survivability to small arms comes only from exposure to them because of short range.
Actually Rak's dies to easily to both small arm and explosions since the crew is to close together.
About the ATG shields:
The cover might only work occasionally but I have seen tank shots colliding with the shield and thus protecting the crew.