With Lowton and Luna, I like 3-5-2. It can be a quite attacking system as well, if you want.
There is no such thing as 3-5-2.
In that formation, the "3" all sit centrally. That means there is acres of space out wide - especially at Villa Park (one of the biggest pitches in the PL). Inevitably, the wide men in the "5" end up dropping to cover the space, meaning you really start playing a 5-3-2 instead.
Having so few bodies ahead of the ball, then, means you end up camped in your own half with your midfielders desperately trying to shut the ball down. When they do, they have 4 other people in front or around them, and 6 behind (including the keeper). The ball tends to go backwards and we continue to play in our own half until, under decent press, we hoof it up to the forwards for the cycle to begin again. This is what we saw in that abomination against West Ham.
I hate the formation. 4 at the back gives us better shape and a variety of options in front. (4-4-2, 4-3-3, 4-2-3-1, etc).
You're right, if we don't control the ball and try to be more dominant. I'd like us to try that against some of the weaker opponents. To me it seems to give a lot of options going forward, and is actually quite a courageous tactic, if played that way.
Whan we're playing Manu and sitting back all the time, what you say will happen. But then it's 5-3-2 all along.