When TOV Hero missions were used at lvl 100, all 4 missions would lvl a character to 110. This has been greatly reduced since last patch. As an example, when a lvl 100 character did Griklor, that character would lvl to 104.XX ... now the same character doesn't even earn 2 lvls.
In the December update, a 200% cap was put on experience earned from a single source. So if you are 10% into level 100, the maximum amount you can go from a single "You gained experience!" message would be 10% into level 102. This is similar to the 10% cap on NPC kills in that some bonuses will allow going beyond this cap. Sorry for there not being a patch note associated with this change.