I guess its been going a while now so the artist will have refined his technique. Plus, Lotto is growing up so he's not the short-arse he was before!
As for the humour, that seems to happen a lot with battle shonen series. At first its all fun and games, but when the power levels reach a certain point it always gets a lot more serious! Such is life!
Jang-Gun released a real monster into the world - an AI with all the worst Lotto character traits combined with Yureka ability to leech off his opponent skills. The end of the (virtual) world is near (again) XD