Build rage fast, spend little on things outside of Rune Overload. And only start Rune Overload when you have high rage (70+ for me usually).
Ways to build steady rage:
1. Get hit.
2. Hit the target with normal attacks.
3. Use Rune Pulse.
4. Trigger Forge.
#1. You have to be the tank and you have to maintain agro as a good tank should.
#2. Hitting the target needs to occur. Should be a no-brainer, but once in a while i stand just a little too far away and use other abilities. Some "melee" abilities have just slightly longer range than normal attacks - like I think Shadowstab is 60 while normal attacks are 50? Might be off on the numbers, but the point is you can occasionally mess this up by not standing close enough.
#3. Rune Pulse can be cast more often by triggering Chain Drive more often. Each Rune Pulse gives you 5 rage and is your biggest damage ability too. Chain Drive has opportunity to trigger each time you land a normal attack, so you should do that often.
#4. Forge buff has to be on. It's annoying to recast every 5 minutes, yes, but you have to do it. Forge has opportunity to trigger each time you land a normal attack, so you should do that often. Each successful trigger adds 10 rage.
Dual wielding for C/R allows #3 and #4 to occur much more often. Worthy Sacrifice has speed 3.0 and Dim Light 1.8. I dual wield those, so compared to using a Catastrophe Survival (2h) with speed 3.2, I get almost 3 times as many white hits by dual wielding. If I were to use 2 Worthy Sacrifice, would have only about 2 times as many white hits as 2h. Speed matters.
While tanking in that setup I can keep Rune Overload up indefinitely. Certainly have done it for over 5 mins, closer to 10. Just use Throw, spam Rune Pulse, and let Rune Overload run. Even squeeze in the occasional Heavy Bash or Shock Strike, but you have to be very careful of using rage abilities. Filler abilities that don't use rage include Shadowstab for damage or Rune Growth for Defense.
Edit: Oh, almost forgot the obvious items: rage potion, Aoth cloak, and the Death Arrives elite for C/R. The above assumes tanking in a group PvE fight mostly -- in siege you'll pretty much have ONLY these items to rely on and Rune Overload thus becomes less powerful.
