the probs : first they are cheap units 110 food and second , they have an average range and also 330 hp is good against halbs :
if u have 20 elephants archers vs 20 halbs = halbs loses without even touch a single elephants and skrimtech not very effective and onagers pretty much expensives vs these archers
The basic problem with indian elephants is.. that they are glorified CA. nothing more nothing less.
Just like korean war wagons....
The issue is that their first function should be as elephants as in to ram in against everything just like persians... and the archers sitting on top should be an afterthought.. Thats how it should work in real life as well.
But no ... here they stop short of any building and just plummet it with arrows.. hopeless.. really.
phew.. its the weakest civ for a DM game for sure.