Yeah, it's a shame the updating pace is like that. I generally only look at the latest chapters and saw it was regularly updated when I read, but in fact it's not when looking at the whole.
As for the heroines, in term of pure power and mana, the MC is stronger, but overall the girls (particularly Senpai, who is supposed to become one of the three strongest character of the game) are strong too. Also, because the MC can only use enchant and enhance magic, he can't beat monsters who need magical attacks to be deal with, so the MC himself says that the girls need to be with him for after the 40th floor.