I see his early game as being a huge hindrance in the bot lane. Yes his Q has some utility, but puts himself at a lot of risk and will most likely be chunked down enough for his mount to run away which prevents him from using his ult. He has no ranged poke, unless he's been damaged and probably won't be very effective as a tank given the "all in" nature of his kit. Best case scenario he will Q, walk in, not take enough damage to be dismounted, and be able to use his ult, but will still be taking a lot of damage after it's all over. He has no way to whittle the enemy down from a safe distance and he has no shields to prevent damage taken while he goes in other than his ult. The most effective way to play him as support would be to ult in for that shield and movement speed boost, but before level 6 and while his ult is down he's most likely going to be dead weight in the bot lane.