It's nice to see people getting good results playing with a very deep defensive line. I often play 4-4-2 diamond at home and away I tend to play 4-1-3-2.
When I analyse my tactic decision to play with a deep defensive line together with high attacking mentality on several attacking players, my reasoning is as follows:
When the opposition has the ball in my half my defenders take up a deep position. From what I have understood mentality decides how often your players will look to attack. So, in my opinion these two tactic decisions can work together in a logical way. The players I have set on attacking mentality will often look to attack the opposition, but when we loose the ball and the opponents take the ball into our own half, then my team will take up a deep position.
IMO, these two things don't contrast each other. I think that some people have trouble to agree with me, because they tend to interpret in a different way what mentality and defensive line really mean.
I don't say I know how it works, but football-wise and how the game works, I find it logical.