If I kill both Raedric and Kolsc ...

[Mungri]

Do I still get quest completion EXP?

[DIIscIIple]

You can tell if you've gotten quest XP in general by looking at the quest in your journal.  If it's bright text then no you don't have the XP.  If it's dull text then yes you have the XP.  I so hated both of those <insert expliciative here> and so did that and yes you can definitely get em both but you have to time it right.