Here is a study of draft pick success rate, by position and by round, using draft picks from 2005 to 2014.  The criterion is, does the pick become a solid starter.  

https://www.arrowheadpride.com/2015/2/20...t-by-round
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1st Round - OL (83%) LB (70%) TE (67%) DB (64%) QB (63%) WR (58%) RB (58%) DL (58%)
2nd Round - OL (70%) LB (55%) TE (50%) WR (49%) DB (46%) QB (27%) DL (26%) RB (25%)
3rd Round - OL (40%) TE (39%) LB (34%) DL (27%) WR (25%) DB (24%) QB (17%) RB (16%)
4th Round - DL (37%) TE (33%) OL (29%) LB (16%) WR(12%) DB (11%) RB (11%) QB (8%)
5th Round - TE (32%) DB (17%) WR (16%) OL (16%) DL (13%) RB (9%) LB (4%) QB (0%)
6th Round - TE (26%) OL (16%) DL (13%) WR (9%) DB (8%) RB (6%) LB (5%) QB (0%)
7th Round - DB (11%) OL (9%) QB (6%) WR (5%) DL (3%) LB (2%) RB (0%) TE (0%)
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From looking at this, since we are in win-now mode and since we want to focus on the running game, I'd pick an offensive lineman in the first round if there is one that merits the pick.  

I wouldn't bother with a QB after the second round.  It's a wasted pick.

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