I thought I'd share the actual resistance of the current event.
I only have one so far. I'll edit as I find the other info and some validation would be great.
Hope this info will help in determining if your resources can defeat Merrow or not so no wasting potions like I did.
Merrow Melee/80% Archer/75% Magic/70% HP/44,284,327
Leviathan Melee/? Archer/? Magic/105% HP/various