Talking from a purely PvP perspective:
From what i've seen on FIveHeroes I think assassins are pretty neat. They're like the "RNG" warrior, they dont just run in and hold shift they play it smart and use their clones/hiding spells for the opportune moment. I'd say they are a success as they're one of the best 1v1 pvp classes for town fights.
Archers I think are good but frankly need work. Nobody has really found a definition for them. They're a single target ranged class... but in what way? burst? high DPS? They bring almost zero utility to the game outside of Portal (which is cool but quite gimmicky/not really needed)
I think the best way to balance them is to make them high DPS based like an assassin, a bit like on FiveHeroes but change the spells to be better combo'd (I like the fact they're reliant on the orbs being max in order to get the most damage out, but sometimes they don't work properly or rather don't coincide correctly) that way, when they're being pressured by a melee class, their dps suffers, but when they do get free-reign and aren't pressured they can destroy their opponent. It would appear tao's have finally found their crux, as archers seem to **** all over them.
ALL of their spells need tweaking and retuning immediately if anyone is planning on releasing a server with them enabled. They scale horribly as it stands, but have great base damage meaning as time goes on they become pretty worthless. DelayedExplosion needs re-cording as it was on FiveHeroes so that the initial hit damage is poor but the explosion damage is massive. It can be purified by a tao, so it has counterplay and imo should be an archers key spell. TL;DR good, can be a success but needs work.
PvE aspect... eh. Both do just as well as any other class.
