Heavily disagree. From a gameplay point of view, Indians are one of the best designed civs, and that is what AoE2 is, a game.
Indians are a fast Boom civ (due to having such a large industrial base in the Middle Ages), and therefore should not get access to either Knights or Battle Elephants, since those units would quickly become abusive, when compounded ith the Excellet Indian Economy (Fishermen bonus + Villager discount + Sultans UT).
Because the devs decided to pull the civ on the eco front, they must have quickly seen how out-of-hand it would go with access to Knights (same problem as BE, too pop-efficient), and decided to remove all Indian Heavy Cavalry.
To compensate, the Camel line was buffed a lot, and this proved to be a prudent decision.
The reality of it is, that Indians are already a complete and brutal package, as far as gameplay is involved, and gameplay is the key factor to any game.
Just look at Company of Heroes 1, where the Axis were massively OP, because the devs wanted to be a bit mor accurate. It was a balance nightmare. CoH2 is much more arcade (gamey) and is the better game for it.
Historical accuracy must be sacrificed for the sake of gameplay, every time, because History was neither fun, or balanced, when it came to conflict.
In fact, it tended to be very one-sided most of the time.