Actually this IS a concern. Martinez has brought in a couple of good signings, namely McCarthy, Lukaku and Bešić looks a shrewd investment (although he initially got Lucky with Lukaku as he wanted Demba Ba and Kenwright was offered Lukaku instead).
But he's also brought in some crap as well. Kone and Alcaraz always looked poor additions, so did McGeady and the Bizarre Traore loan was a complete farce.
Cleverly looks nailed on and for some strange reason Martinez seems to really rate him.
Notice Cleverly was an unused sub this weekend as Villa have also come to realise his utter gashness.
His transfer policy looks ropey to me to say the least and when you're in a situation where you get little support from the board and rely on really shrewd signings for modest fees, then that needs to be an Everton managers strongest point not a weak point so that's a concern.