#1 - March 1, 2009, 3:14 p.m.
For clarity: Your and your linked veteran character are partied and within 100 yards of one another while the quests in question are being completed? And you, specifically, are not receiving the triple experienced (as your veteran question does not appear to be on the quests in question, he/she wouldn't be eligible for any experience upon completion)?
If so, may ask if the quests in question are green to you presently? I ask as, if they are, they may be marked as "Low Level" or show up as gray in difficulty to your linked veteran, a fact would cause neither you nor your linked veteran to qualify for triple experience.
Also, what does your Combat Log entry say upon completion? You may not wish to trust any scrolling combat text, as, at times, what's displayed won't account for added bonuses.
Thanks, Darkevil! :)