Well no need to actually play with him, With three attacks it is very likely to roll only one 6, and then Rumil can potentially force it to re roll, and most likely it will not be a 6, and "WUPA-DEE" the good side wins...

_________________
I am the Mouth of Sauron, here him speak'

It's not quite that simple though, if you know Rumil is likely to be the biggest threat all you have to do is kill him before the combat or during it. Use might to gain more than one 6 on your first combat, winning any ties and then focus all 3 attacks on Rumil, needing only 3s to wound the chances are you could take him down over the course of a turn or two depending on your luck.

yeah but of your army has Gil-Galad and Rumil then it would be pretty hard...

_________________
I am the Mouth of Sauron, here him speak'

There is only 50% chance of getting a 6 with 3 dice so I wouldn't rely on him too much. A bunch of Khazad guard and Durin I reckon could take Sauron out as they will all pass terror (bodyguard) and S4 and 2H weapons as well as Durin's automatic +1 could probably take him out.

_________________
"War does not determine who is right, only who is left."
- Bertrand Russel

Add Rumil to that, is basically impossible for the Dark Lord to Survive then...
POSIIBLE but suicidal

_________________
I am the Mouth of Sauron, here him speak'