Ronove's shield is only 35%. That's the equivalent of a 1.53x boost to HP and to RCV. Barely better than Ra Dragon's, but RaDra's team has better stats to cover the 0.03 difference. I'd have to crunch the numbers again, but IIRC, Ronove's RCV is ~10 points better, while RaDra has a modest HP advantage (500 maybe? It's definitely <1k). Kaede and Myr are the ones with the crazy shields. RaDra is just as survivable as Ronove in terms of raw numbers, but is practically more survivable, since your defenses don't vanish when you have only 4 hearts on board.
Damage reduction from heart cross behaves differently than HP multipliers. Example, say you're playing the Journey to the West Dungeon. On the Bajie and Wujing floors, the HP reduction moves performed by these two (especially Wujing if you try to one hit KO him without something like delay or poison) would be much less of an issue against Ronove's shield since the HP reductions would be reduced.