Yeah Viyajanagar is the major pain. Pretty much no matter what I do as one of the smaller factions I'll inevitably get taken over by them and attacked by their inevitable chain of allies. The problem with Delhi is they have a lot of rivals on all sides though I have yet to give them a go.
I took over entire India as Delhi, your only chance is to ally Deccan and support them in their wars, not to little, 'cause then Viyajanagar becomes a superpower and you're doomed, not to much, 'cause then Deccan becomes a superpower and annexes Gujisomething, gotta pay tribute to Timurids, annex Bihar instantly, never allow Chagatai to take actual Delhi, and kick Rajputana whenever they're down. At least that was my tactic, I still only barely kept Deccan alive and if I hadn't gotten the last core and formed Hindustan I'd have been fucked.
BTW: Wanna do a multiplayer game in India some time? People mostly prefer Europe and the Middle East.