This is one thread on it
Mystic Dexer build, Throwing or other weapon skill?
This post by CorwinXX sums up the difficulty
I have a mystic thrower.
It's difficult (impossible) to get 3 FC + 6 FCR + 50 EP + 45 HCI + 45 DCI + 100 DI + 45 SSI. (You need 3 FC to have 2 FC with Enchant on)
As a result he is not a good caster (low mana, low MR, low SDI) and not a good dexter (low DCI, low HML).
When I use RC I can't use AI because I must save mana for MS (mass sleep) + RC combo.
I must always check is Enchant on and recast it when it wears off (you can't prolongate Enchant). Often I cast some spell and auto-unequip my weapon giving to monsters incredible chance to hit.
I don't use Stone Form because it makes me too slow.
I needn't to heal when I'm not under attack and can't use CW (healing) when I'm under attack because it's too slow spell. I can't use Healing Stone two times in a row so most of time I use Chivalry to heal myself. It's also not as fast as it could be with 4/6 (but you can't have 4 FC when you've got 70+ Mysticism).
So most of time I don't use mysticism. This means my char has just 4 skills that I use.
I haven't enough HML to chain AI. (I haven't mana reduction)
I haven't Bushido so I can't do much damage when I haven't slayer.
With a mystic thrower it's easy to kill not so hard monsters even with bad equipment... but even with high-end equipment you can't kill hard monsters (or crowd of monsters). So it's a good char for a new player... but not a powerful char.