Priest Booster.

[Entaroadun88]

I have a 70 Priest on my main account.
Would he be a good booster? The only AoE is Holy Nova ('http://www.wowhead.com/?spell=25331').

[Svpernova09]

For lower levels, sure, but the higher levels you'll have to do smaller pulls because clothies are pretty squishy against the mid range groups.

[elsegundo]

at higher levels i suggest not using holy nova unless your boostee's are tanks, then you can simply heal+dps while your boostees tank. of course, you'll have to experiment.. but for instances up to sunken temple even, you should be ok.
also, there's a glyph that will give 50% more damage to your holy nova while healing you for 50% less, so something like that. i'd use that for more dps while not overhealing.