I personally think priests are the hardest class in the game to kill once geared (with the exception of bubbled paladins (which my priest can dispel)). I use a priest on my team and he brings some major stuff to the table. Fort alone is worth having a priest in PvP to help buffer the team against huge hits and AoE. Mass dispel and fear only help and if you PvP gear at all priests can become rather ridiculous when you consider they have a multiple DPS bodygaurd squad with them.

Level 70 will have plenty of content if you do all of it. There are a few things to consider if you don't have Wrath

1.) You won't likely have the option to raid....ever. If your level cap is still 70 it will be hard to find groups and you won't be able to solo any raid content.

2.) PvP will not pop as often due to the level 70's being few (and you might be in a bracket with 70-79 which would suck for the 70's.

3.) with wrath talent trees out most 70 content will probably feel too easy.