Well, the rate from killing mobs with Sanction up is 10% of xp (same as other similar point systems). It can stack steadily if you are picking the right targets (especially now that you get double xp, and the bracketing has been revamped for post level 75). The trick I guess is knowing where to find the higher level mobs they added a while back (the 85+ targets they added a few years back deeper in the outlying areas, NOT the lower ones closer to town--the 10-15+ difference in levels has a profound impact on the xp). This could double your return (if not more) with the tweaking they've made to experience point acquisition.

Alternatively, you can try hitting some besieged. You now get up to 15k Exp and 5k IS a pop for full level 8, and at level 99, there is little excuse for not capping your besieged rewards.