couple questions on lvling and suchFollow

ok so i had quit WoW a couple months ago, for various reasons, but my friends have convinced me to start again. I figured as long as i was on my offseasons anyway i might as well... anyway

i had played a mage before and had a rogue alt i loved. when i come back i think ill make my rogue my main for the time being. My general plan is to begin from where i left off with it(About mid-20s, never played it much) and lvl with a general sub-ambush build. I mostly do instance grinding and some questing if i hit good lvl ranges or reward areas. Then i was planing on switching to mutilate either right at 50 or 60 and PvPing with sub at 49 or 59 consecutively.

Is this viable? And would it be better for me to switch to mutilate right off the bat at 50 or do alot of PvP at 59 and switch at 60?

Another note. I have tried combat swords for lvling, and while i got slightly better results, i felt that it took less skill and was severely bored, so i would like to avoid that unless it is blasphemy for me to do anything otherwise to lvl.