here is my suggestion on how to do rim:
Use buff pots: Cocktail / rose / event dish / dragon / beer
get your toon in party with all your buffers. You need to get POM + Crippling or Assault cast on you right as you proc your cloak buff on the NPC.
Once you have cloak, pom, assault, log out to the character select screen and set a 5 minute timer.
Tip: You can also get GoG buff if you are a mage or p atk crit dmg toon, this will help but u need to be very fast to get that buff, proc cloak, get pom assault and be at npc to log out without wasting too much time. you can do it, just prepare to do it correctly.
Every 30s or so, click your toon so you don't log out.
After ~5 mins, log in and go into rim kama. Be sure to target whatever has a green name above it's head first. The exact time of this delay is dependant on each person's buff times.
Tip: Cloak proc runs on 10 min cool downs. it hits for 2 mins, then after it fades, there are 8 mins that pass before it procs again. this time ticks down regardless if you are in game or not.
Your 1st 1:30 should definitely be with cloak pom and assault and gog
Up through 4:30 will be POM + Assault + GoG if you have it. POM + Assault can be considered a cool down because it gives so much dmg boost.
Tip: do NOT use a special dmg cool down until after the 2nd cloak proc is gone, unless the skill will be up again when 2nd cloak wears off.
4:30/5:00 - 6:30/7:00 should be 2nd cloak proc.
7:00-8:00 use abundance
8:00-9:00 use dragon shirt boost
9:00 - 10:00 brooch br and other class cool downs.
this is just the basics and doesnt take into account the special class dmg increase skills. These should be used after the 2nd cloak as needed to max dmg. you can use them before but make sure you have them for your last 3-4 minutes. That's where you will definitely need them.
the entire key to rim kama is keeping boosted dmg for the maximum time possible (10 mins in this case). pom + assault cannot be ignored for lower geared toons as a way to sustain dmg if you enter with these buffs.
once you have 200 fragment things, turn in for the top grade la vies to make the instance easier. those should be purchase #1