I have been playing WOL for a while and I always had issues playing against Indians in the game since they have a good economy they can Spam hell of Elephants and crush you in seconds if you're not prepared to stand ride :v
But I found a couple of weaknesses they are even though hard units and stand a lot of fire from infantry they are pretty much sensible to units like the Maceman by the dozen and a mix of light artillery and some Chetniks to hunt down the Ghurkas and sepoys that protect them
Plus if the spies can't slow them down and break their lines so it's easier to get rid of him
as well it's important to raid as much is possible their villagers
My advice if you're playing serbians try to advance to second Age by sending most of the villagers to food and a couple to wood if you have on your deck some Maceman carts that will help you a lot and keep you villagers as much as possible to avoid raidings from outside the city walls try to use the Economic units on your favor , some war pigs and gooses and farms will keep the economy really up for the late game and sent at least 10 villagers to the beehives so you won't depend on mines .
Mines planted by spies help a lot if we'll placed
And try split your units in this order
Maceman on front for elephants
And seimen and Chetniks behind them
If you have Koljaniks try to surround them on the back and use your Light artillery to bombard their Ghurkas and sepoys
If on sea map try to use the economy cards for sea some mercenary privateers plus the sea card that allows you to have more warships and some extra dock and prepare to defend your sea (Chaikas can fish :p )
Batle of Kosovo card if you want to have advantage of your dead units .
Voivods make increase a slight difference on ranged attack units if you have some
That's it I hope some one find this helpful