2 and 3 box question

I got the following characters and I was wondering what your opinion would be to use for the "main" box for certain scenarios:

- 70 healadin + 70 warrior for pvp and to use as part of instance group - which would make most sense as main box?

- 70 healadin + 70 hunter for doing hard quests and part of instance group - and maybe some pvp - again, which would be main box?

- and all 3, 70 healadin, 70 warrior, 70 hunter - primarly to run easy instances and to be the core team of an instance group - which would make sense most as main box (in all cases the warrior would be tank)? Is this setup viable for pvp?

Thanks!