The difference in item level between a 101 and 109 is not that much. My 101 in 840-845 epics and quest gear to fill the remaining slots has item level 810. My 109 with comparable gear has item level 830.
Just a few things to note. Item level 750 and below gives a 0% increase in stats inside a BG. You get a 1% increase in stats for every 10 item levels above 750. If you're a 101, you need to be in BOE epics to get above 750. You will not be able to get above this threshold with quest gear. A 109 can get about 790+ with just quest gear. The game doesn't round up. Item level 810 and 819 both give a 6% increase in stats.
Class hall missions give 150-165 AP with a chance for an extra 150 AP. They don't pop every day though. After doing all the legion quests, looting all treasure chests and killing all rares, I think I had like 15k order resources. That will last you a long time if you only spend them on AP missions.
Advantages of a 109
- multi-spec
- can get away with only using quest gear
- more options to get AP
If you're planning on buying epics and your legendary, then there is not that huge of a difference between a 101 and 109 as far as performance inside a BG. And as someone else mentioned, if you go 109, level to 109 first before you do any quests or kill any rares that drop gear. If you're going to level to 109 playing BG's, then save all your crates from wins and open them when you are 109.