Hi.
E222 isn't really a bad location. One thing to consider about being below the dining room is that the dining room would usually be closed during the time you want to be sleeping and it isn't like you're above or below a nightclub where there's loud music (as I was a year ago on the Victory). I had the same concern a few years ago on the Disney Wonder when our cabin was located right above the theatre. Turns out that when there was something going on in the theatre I was at it, not in my stateroom so all was quiet by bedtime. On our upcoming cruise on NCL Star our stateroom is right above the art gallery. Again, I am not concerned.
The upside of your cabin is that because you're toward the back of the ship there will be very few people passing by your stateroom in the middle of that night making noise and to me that's a plus.
Enjoy :beach: