Thanks guys! Much appreciated.
Moby Dick is really only worth it if you have whitebeard right?
Like both ElChado and Clogger mentioned there is definite use across other teams outside of Whitebeard. The 50% HP cut can easily be made up with decent RCV. I haven't used the ship yet myself, but I'll definitely give it choice over Merry in the fortnights to come to see how it works out.
i tried for a while when it first came out but i noticed every time i got to stage 18/19 my alvida had 2 turns left. I wondered when it would hit me for not maxing alvida and i guess here it is.
I'm doing this off the top of my head and am assuming you went with a Whitebeard team. But your Alvida might be workable, you'll need to use it at Blamenco early on and then Vista. I can't remember the turn counter between those two stages as it does vary, but I feel it should be workable. Although, if not, you could potentially try to heal enough to take a hit from Izo and then proceed from there.
The key would be having Alvida ready by Marco and if by some luck him having a 3 turn counter on his appearance. Otherwise, in order to make this happen you'll need to dance around on the Jozu stage and a good way to ensure she'll be ready is if you can tank his 6,700 ATK at least once. But that's dependent if you can heal enough with meat orbs and still farm a green orb on Mihawk twice to finish him off.
Once you pass Marco, you'll need to hang around on 19 for as long as possible anyway, up to 17 turns to reignite the Whitebeard and Mihawk specials. Worst case scenario it maybe only 15, but that's the bare minimum you need to stay there regardless. While it's anomalous, I have been able to heal here to full HP to tank a full hit from Blamenco at 13,680 ATK and this is something that may help you in your run as well.
Once you get to 20, you only need 6,000 HP to survive that stage total. Whitebeard will do his 70% HP cut on you, then you have 3 turns to beat Jozu/Marco. The 2x Whitebeard specials and Mihawk special will do wonders damage wise. Then it doesn't matter who is activated first, to tank Whitebeard's attacks. It's simply the HP, Perona will eat the 2,000 and Alvida needs 4,000. And right before he's able to attack a third time, you'll have GP Usopp ready by that point to finish the job.
What I did early on in my runs is map out the forest, based on what I knew for turn counters both worst and best case in relation to my unit's own special cooldowns. It could help if you decide to go back in.