I just defeated Ketheric being lvl 10. I read people are 8-9

So, I'm one of those who tries to do everything and complete all the quests. I just defeated Ketheric / Myrkul while being lvl 10 (I got it while exploring the mind flayer colony). I read on forums that people usually do it at lvl 8-9. Won't it be much more difficult?

P. S. It is a bit sad that I have only two levels to earn during the whole third act.