I have over 70 hours in game and beat the game on all four heroes. You will be around level 21 on first first play through and here is is the skill order and weapons to use to best beat the hardest content.
Timestamp:
00:00 Dev Intro Great game
00:49 Skill order best for beating Dusk to Eclipse
5:08 Arc Jav is OP short cool down
6:57 Weapon Load out and why
9:16 Weapons to use on special vamps works for rooks too