You can't really compare the Twins, because it is a specialized boss that is weak to ice. Not all enemies will be like that... in fact some will be healed by your ice/water spells.
The rogue does need some buffs to do well, e.g. desecration, wildfire, but benefits more from the buffs than most other classes since their base attack is only 2AP.
In the beginning it's a struggle (like any hybrid character) but I find rogue/magic hybrids more efficient than pure caster classes.
