You can vendor train both Mystic + Assess to 65%
Mystic will occasionly roll apon the use of related skills (magery) however I'm talking about several minutes inbetween actual rolls, making it impossible to actually raise
Assessment requires active use to actually raise, you could raise it via combat sparring to around 70% at which point you would have to actually macro it for the rest
The bonus's mystic offer to magery, and assessment offer to combat are still functional, you just can't actually raise them past the amount you train off vendors
To summerize, if you are lucky enough to have already gm'd them on your character, do not nuke them