We had a really long discussion about this about a month ago. Rather than reiterate all my points, I'll just link to that thread here: viewtopic.php?t=436821
A quick summation of my thoughts on this:
-Drafting the preseason #1 and #2 WR doesn't actually net you the #1 and #2 WR, or anything close to it. In the last 6 years drafting the top 2 WRs would not have netted you the actual #1 WR a single time, and WRs drafted in the top 2 are far more likely to finish outside the top 5 than within the top 2.
-Historically, the bust rate of late 3rd/early 4th round RBs is around 75-80%, so to REALLY make this strategy work you need to grab RBs in the 3rd, 4th, 5th, AND 6th rounds, not just the 3rd and 4th like people get trapped into.
-This draft has the potential to make you weak at EVERY position. Your RBs, obviously, are going to be far behind. You QB and TE are going to be behind because you have to use so many mid-round picks on RBs. And I'm not convinced you'll end up with the best WR corp in your league because you won't be drafting your WR3 until VERY late so if one of those top 2 WRs doesn't perform like a top WR (and history suggests that at least one of them won't) you have little depth there.
If you have the foresight to know exactly which WRs are going to finish as the top 2 and know exactly which mid-round RBs are going to break out and know exactly which 7th-8th round QBs/TEs are going to break out then this could be a great strategy. But if you have that much foresight then you're going to win your league regardless of which positions you draft first.