So I'm new to LotR/Hobbit (local group has formed due to the "death" of Warhammer). After playing and watching a few games, I have a pretty good grasp on general tactics. My group I think is making 650pts the standard play size, and considering what I have, that puts me in a bit of a pickle for list building... Here is what I have:

Amdur, Lord of Blades x1
Easterling War Priest x1
Easterling Captain on horse x1
Easterling Warrior w/ sword+shield x16
Easterling Warrior w/ pike+shield x15
Easterling Warrior w/ bow x16
Easterling Kataphrakt x9
War Mumak of Harad x1 (w/ 1 Haradrim Chieftain, 12 Haradrim Warriors - 6 spears, 6 bows)
Banner x1 (no model, just a loose banner I can put on someone I guess)

I haven't used my Mumak yet, but doing a variety of list-building tests, it usually comes out to 3 warbands, something like this:

Amdur
Warriors w/ pike + shield x12 (all upgraded to BD)

War Priest (solo...)

Mumak w/ Gnarled Hide
Chieftain
3~5 Haradrim Warriors of some sort (bows, upgrades, etc)

So my question I guess really is, what's the best way to outfit my Mumak if I want to stick w/ that Amdur Warband and still have a War Priest in my army? Is Gnarled Hide as mandatory as I think it is? Should some Haradrim have bows? Or just a couple spear warriors w/ rocks? If bows, should I upgrade them for the +1 to hit? Should it just be the Chieftain solo up in the howdah and spend more pts on troops to support the War Priest? etc etc.

Any and all input is appreciated!