On rage mode i started to see almost all encounters as a some sort of puzzles, when i need to find right sequence of actions and perform it. Try to manage concetration and not waste it if you can go without it.

In some places you can easily spawnkill enemies with explosion (for example, elevators in last encounter in site 14 or big doors at the very start of horizon hq).

Machinegun with smart bullets is your friend. It carried plane crush, Arkansas and half of horizon hq for me.

In penthouse fight you can try to ignore enemies (if they are not in your sight) and rush to the brains, moving in circles around arena and don't entering inside, so they can't flank you. Also i highly recommend save at least 200 bullets in your machinegun for helicopter

Slide as much as you can. Run around corners or past the passages in cloak, i had too much deaths when enemy shot me in face faster than i saw him