How to heal large pulls in stormblood as whm

[Taika]

How do people spam holy in those large pulls? Every time a tank pulls large in a level 70 dungeon, if I cast holy the tank is usually loses 60-70% of his/her hp by the time holy goes off.

I posted this earlier, it's pretty much how I heal bigger pulls too:

I took a video of an expert run of mine the other day in case that helps: https://youtu.be/M18vqjQtp9c

I got Ala Mhigo and the tank wasn't doing the biggest possible pulls for that dungeon every single time, but from my experience the pulls she did were usual for that dungeon (for bigger pulls, same principles apply, but you will probably have to use Cure II more between Holys). I'm not very experienced with WHM in SB and I don't remember the expert dungeons that well, so my play there isn't really optimised. My WHM is currently i313 and the tank seemed to be wearing mostly i310 stuff.