give warmogs malphite like passive
if above 75% health receive a 200 strength shield
The shield will refresh if the champions has not received damage in the last 9 seconds.
or could maybe refresh by 100 points afer 4 seconds out of combat and by +20 every second thereafter. up to 9 seconds total for 200points.
this can vary could also be: 6 seconds for 100 points and +25shield strength per second up to 4 more seconds.
I get the need to nerf the overall hp on warmogs, particularly with cinderhulk and hp scaling spells benefiting so much from it. But I think a way to keep warmogs relevant without having it give so much raw health is to have it give you a passive shield designed for your initial engage.
Increase its cost by say 200 gold.