First and foremost, you should always draft for value ahead of position. That said, it's also good to pay attention to who's coming off the board by position, so keep a cheat sheet on hand. I agree w Anthony, you have to get a solid RB in the first two rounds in PPR--then shoot for the best available WR/RB in 3/4. I'd try and take a QB in the 5th since this is an 8 man league.
I'm not really a fan of waiting too long to get a solid RB, and by the 4th or 5th round your taking risks. However, if it's only an 8 man league, it really depends on when you draft. If you pick 8th (assuming snake draft) and go WR / WR, QB, let's assume that picks 1-7 will take their 2 RB's within those three rounds. You'd be looking at the 15th best RB (depending on your list Stephen Jackson, LeGarrett Blunt, Amad Bradshaw.). Also, consider that by round 3 if you go to take a QB and the top 4 QB's are already gone, the 5th ranked QB last year and the 8th ranked QB are only about 25 point differential....so you'd be better off taking a higher ranked RB in round 3 and waiting a couple rounds for a QB. Again, it all depends on what number you draft.
I agree with Keith. I would assume by your first pick the top 5 RBs have been taken, especially if this is a 4 point passer TD league. The difference in EV from the top 6-10 RBs is similar to the EV in the top QBs (1-5). I may look at Rodgers here and then take a 6-10 RB on the way back down. Not taking QB and going RB RB potentially sacrifices a top 5 QB and the consistency he would bring if there is a run on QB's during the next 12 picks. However, depending on how smart your league is, you could get away with picking up Brees, Ryan or Freeman as your 3rd pick, and have two top 6-10 RBs. Alternatively, you could take a premier QB most likely, and secure a top 6-10 RB and on your 3rd pick still potentially land a 6-10 RB again. Either way, personally, I'd stay away from the WRs in the first three rounds, unless it is PPR.
You need to remember that RB's are your workhorses in all point systems (even PPR, just because it is a PPR league doesn't exclude all the RB's. It definitely changes the system but pushes a lot of reception RB's back up). I usually draft RB, RB, QB, WR or RB (depending) then RB or WR (depending on what the last pick was) then WR. Let's leave it at this, would you rather have a RB1 at flex or a WR1 at flex? An RB stud is a sure thing, WRs sometime do not get targeted even if they are studs, depending on the defense.