Hmm... but crit chance on weapons also affects spell crit chance (with savage sortilege)... so rogues that use magic still suffer a damage loss
That would only apply if you made a rogue (points in FIN doing physical damage) that wanted to do magical damage using Fireball or something (requiring points in INT).
That would be a terrible build.
Rogues do physical damage. Even the rogue skills that do magical damage are mostly not that useful. You should put points in scoundrel to boost movement and perhaps a few in warfare/huntsman for the skills in those trees that also backstab with guaranteed crit (battlestomp, crippling blow) or are useful (tactical retreat).
All of your attributes should go in FIN with minimum MEM and perhaps enough WIT to go first.
There is no synergy at all between FIN and INT and having savage sortilege on a rogue would be waste of a talent. Better to put it in duck duck goose or executioner.
If you want a hybrid physical/magic character then ranger or (better) STR/INT battlemage would be a better bet than a magi-rogue.