I'll try not to go into a long winded dissertation here but. . .
Sometimes I need to cut quite deep with a very small endmill, think .5 deep with a 1.5mm (.059) end mill to get good detail and crisp edges. I have found that if I make that cut after clearing out material I have all sorts of problems, deflection, bit breakage, etc. What does work is to make those cuts first. I use bits that have a very high spiral that helps pull the chips out and prevent packing. Also make sure the dust collector is running for the same reason. At the same time that technique helps prevent chipout at the surface by larger bits.
"If you see a good fight, get in it." Dr. Vernon Jones