His pressing is absolutely critical yes, but not so much the tracking back. Its his pressing high up the pitch that is so fundamental to how we play.
And I don't agree with Palmer doing little off the ball. He has more tackles per game than Allen this season (and O'Hare, but small sample size obviously). More blocks, interceptions and fouls too.
His tracking back is really important. You won't find many who disagree with that. He'll regularly drop back when the opposition has the ball to add an extra body in midfield. It's pretty vital to our counter play too. As he's shown on numerous occasions.
Granted, Palmer can tackle when he wants to. But I'd air to the side of caution using those stats to press your point. I also wouldn't exactly use Allen as a benchmark.
I just don't know what else he's particularly good at as he lacks all the attributes you'd expect from a CAM. He's slow, his movement is by large poor, his passing is dreadful, as is his decision making, he's wasteful and he clearly has a fitness issue.
Realistically you have to wonder why he's been brought in.