Why are people sleeping on Reinhard?

Super fast SA animation (probably the fastest) and he gives everyone 100 burst arts. Multiplier is low, but with the amount of times you can spam his SA, his dmg will skyrocket. He should be played like Hkroy, just ignore his NA and TA and spam his SA. He basically gets his SA every wave (not hard at all to get another 100 arts). He also has great slots and we don't know what his TW does.