1) Hashirama is using clones now so he may not be able to use shinsuusenju while dividing his power amongst his clones. Considering he is fighting Madara WHILE having a part of his power used by his clones I'd say he is doing pretty good.
2) Madara isn't dropping meteors with Tengai Shinsei because this jutsu is risky since it's suicidal and it takes time for him to regenerate once he uses it. If he uses it, a S/T user like Minato can dodge the meteor and might seal him while he is regenerating. Another risk is that while he is regenerating, Obito would kill him and Madara can't defend himself at all.