The immunity shield exists for few seconds, it gives all visual clues similar to boss mechanics in MMO. It certainly plays its role when almost dead tank meets another in open field, but do you have many situations? If you see shield, why not treat it as full HP tank for a moment?
There are few vehicles which can use super aggressive tactics because of their good burst potential - most prominent are MT-LB and Pindad. The majority, other vehicles can give one or two shoots and then they die anyway with 1 HP left.
I suggest look deeper in problem, does it apply "p2w" factor to each vehicle, to each mode? The burst IMO is a main problem here, and if devs can fix it, the kamikadze runners won't exploit Ophelia skill much. Second problem is how GLOPS with its multi-respawn "strategy" works, because it simply multiplies problem with Ophelia perk over and over.