it's a very good point, the dizzy ability can be annoying if you're about to receive strong atk.. but if by chance that the enemy is dizzy, he'll have both gaia and perun as well as arc, so he can use their def one instead..lower chance that she'll be dizzy twice in a row, but then to use either 1 that's left..by this time, 3 turns would passed, and then 2-3? more turns for her next strong attack and that's if she's not stunned by that time.. so really by then, the ability cool down or whatever and he can use them again.. this is just worst case scenario anyway..
the battle seems fairly easy with the right defense, so he's going about it the best way, and with the 3 tank partners he may use the battle shouldn't be too hard... arc would be betterin myopinion cause she heals too, even if it's just regen for 3-4 turns.. yggdrasil regen too, but with the amount of thunder hp weapon he can probably do it without a healer, as i have seen others do it without one and he's stronger than them XD
froom what i've saw, her raging strong ability deals 3-5k? to 3 partners, and normal one deals 2-3k or so to all.. though i may be wrong, and don't know if anyone already said it in the thread.. she have no buff to herself, but in normal one give a debuff to allies which i do't know what it is.. someone else probably said i'm sure gaia may die pretty fast though since she'll have lower hp than the thunders..
my advice isn't the best like i always say, just saying my opinion and hoping maybe it can help