The only thing is, how can it be a panic buy if it's not replacing the players who left?
Arteta and Park were the only real replacements- and I suspect they'd lined Arteta up for a while in fact, so hardly panic! On second thoughts, I agree about Park, but I still think his transfer was so odd considering what's happened since it goes beyond that!
Yeah, there are mixed opinions about Mertesacker, but he was brought in to shore up the defence- this was not a problem caused by the loss of Nasri and Fabregas- again, can't be classed as panic when it was obvious they had been trying to do something there anyway. The Arsenal fans that don't like him are those that feel he is too slow- that's fine, but as a defender he is very good and both the fans I know have said they really like him just because he is different to what they already have. It was no surprise to me that Arsenal's good run of form up to Christmas and over New Year coincided with Mertesacker finally adapting to the physicality of the league. Their form dipped after he got the ankle injury that put him out for the rest of the season. If he hadn't got injured, who knows?
The whole "starting eleven" thing isn't really fair though- Santos is pretty much guaranteed a space on the bench and finished the season strongly. Mertesacker is a player that will start against certain teams- some Arsenal fans were calling for him ahead of Vermaelen because they see the latter as a liability- and will be on the bench others. So they are both in and around the starting line-up.
Don't get me wrong, I don't think they are great signings, but I really don't they are as bad as people seem to think. Mertesacker's record speaks for itself.