All I have been doing is cautioning against using 4.6 YPC as the baseline for his production.
I can agree with that. However the difference between a 4.6 and a 4.2 or even a 4.0 YPC does not have as significant an effect on how I value the player as others.
For example, I still rate Mixon pretty high despite him having a comparatively abysmal 3.51 YPC last year.
As someone pointed out earlier in the thread, the difference in a half yard in YPC over a season is not tremendously significant for fantasy points.
Where the 1/2 yard change in YPC does matter is if it threatens the players total touches. Enter the threat of Kenneth Dixon. However, comparing the rushing statistics, I am not sure Dixon looks in any way superior Collins as a rusher.
First, the complaint about using 4.6 YPC for Collins is because he had a great YPC as a Change of pace/rotational back that dropped once he was the feature back. As pointed out multiple times in this thread, it is expected that change of pace/rotational backs will have a higher YPC.
The only stats we have on Dixon seem to be from when he was a change of pace/rotational back. If we are being consistent, his 88 for 382 career (all from 2016) 4.34 YPC should be compared only to Collins 37 for 261 (the four games when he was a change of pace/rotational back before he became the feature back) that yields a 7.0 YPC. At worst, if your are comparing results in Baltimore you have to use Collins 4.6 YPC.
HOWEVER, there is one big wrinkle and one small wrinkle. The big wrinkle is that Dixon got his 4.34 behind a healthy Yanda and Baltimore line while Collins got his behind a line missing up to three starters including Yanda. The smaller wrinkle is that Dixon's stats were as a rookie whereas Collins has had a couple of years of sideline seasoning. I saw this is a small wrinkle because unlike other positions, the RB learning curve for rookies as far as rushing the ball is much less steep.
I have been worried about Dixon primarily for his pass catching skills, but if they are truly happy with Collins skills as a receiver, I think Collins has a very safe lock on 15-20 touches a game for at least the first 8 games in 2018. I would be fine if those yield a YPC of 4.0 if he holds on to his red zone role he assumed in the later part of last season. In a given game, the difference between 20 rushes at 4.0 and at 4.6 is 80 yards vs 92 yards... or just over one fantasy point.
Finally, I think the decision to pass on an RB in the draft shows Baltimore confidence in the entire stable of RBs. The have a starter, back up and change of pace they are pleased with. You can decide for yourself who they currently envision in each role.