I had to look at the date on this because Chimaera's ultimate no longer heals all allies since the ships 2.0 rebalance, just target ally.
But yeah, ultimate abilities are meant to be powerful, and Chimaera's is definitely one of my favorites. But Tarkin's vs. low level ships can also annihilate a lot of people. Ackbar lets all ships go twice in a row with specials. Malevolence outright stuns your capital and prevents your ships having any protection for the rest of the fight. We don't need to talk about Holdo who straight up destroys the enemy cap, because there is no team currently to justify using her.