Should I ditch my mage?

Well I just learned that Archmages are useless for bossing

Not useless. Less useful. Many many archmages (archmage meaning 12x and 13x+) can solo pap so you have no pap worries. The problem is, if you quit a mage, can you level another character to 8x, 9x, 10x? Because nothing can train as fast as a magician character. 1st job, magic claw's built in mastery made them fastest. 2nd job is debatable but they're definitely not slowest. 3rd job, and 4th job, the magician wins in terms of leveling speed.

If you make another character and can grow to a bossing level (12x+), sure go for it.