Honestly, anti-GB missions are only “op” because the rewards from GBs are just too high. They went from 100k in Cards to 600k per explosion. Cruisers and battleships remained the same in terms of profitability until kaz jacked the profitability for cruisers up, presumably as a test, and brought Battleships back into line with how profitable they were before.
Dropping profits for GBs to around 300k should fix the problem and encourage players in heavy caps to try and pick on ships their own size.