2 GK
1DC/DL
1DC/DR/DMR
4DC/DMCs
2 MCs
1 AMC
1 ML 1 MR
3 ST/AML/AMR

Allows me a variety of formations and unless a really bad run hits, gives me no worries from injuries. You can use nearly all formations without OOP with this 15.

When I'm fighting in all 3 competitions, max squad is a must and i tend to use the lessers in 2nd leg cup matches i'm already up by an extreme amount, meaningless CH.league matches or league matches vs the bottom 5.

As to your question, whether to keep 4 mcs depends on your usual formation. If you are usually playing a 3-5-2 Flat for instance, i would keep 4. If you have aging players, and up and comers of the same Q rating, play the oldies and train the youngsters. Personally, I have had to sell players that picked up a crucial card ban at an inopportune time so keeping 4, seeing how midfielders get more cards than average, would likely be a good idea, especially if you are still in cup and CL.