We've done it before. Vlasic as stated - that was bloody ridiculous. In no way should one performance dictate a signing; there should be a raft of info and research behind every signing, and if they're not available you go down the list to find similar.
Hell, we did it with Fellaini famously - a last minute massive punt as we had money and he played well against Liverpool. It's just lazy - even if it comes off like it did with him, it's just blind luck. It indicates no serious system is in place.
With a DoF, you'd have hoped these amateur hour things were done, but no, we're even worse with it.