One thing I've noticed, I'm level 82 with a power of roughly 30,000, and if you can't beat the seal then you need to either back off and grow stronger first, or skip the seal and come back later. This strategy is actually quite convenient for the main plot pauses you reach later in the game where you have to reach 1-2 levels higher before you can continue the story. Trust me, take your time and milk every drop of power from every level you can, seals will become easier and you will become more competitive with the higher power players.

lvl75 bp:28k still can't beat my seals because hey're lvl83 wuth so much hp and attack dmg