So, I have nearly finished painting my dragon. It has a nice purple bottom color and carmine red scales + other areas. I also used a lot white/bone color... It's claws and teeth need a bit fix, then maybe a few overall fix, after that I guess it's ready. ^^

Themic is briefly next: A young, yet magically powerful dragon has awakened and is gathering army. Spiders, orcs and all kind evil creatures around join him. The dragon thinks he is the true lord. He captures and kills all messengers and patrols of sauron. Sauron decided to use this and made up a plot: he sent an orc patrol, which was informed by both rumors and "official" knowledge that the wizard Saruman had a powerful ring which would drive all his enemies into darkness. Dragon's forces caught this patrol and found out this information by torturing with spider silk and orc whips. Sauron's sacrofise of hundreds of orcs caused resolt, as Dragon decided to attack Saruman. Sauron thought that the old alliance of Angband between dragons and Sauron should be viable at least later when the dragon grows and wises a bit. While who would trust the douple betrayer called Saruman. Also, elves are causing bad harm for Dol Guldur, this dragon comes like a gift...

Something like this army list would work?:

*Dragon, wings
-4 giant spider
-6 warg rider

*Orc Taskmaster
-12 morannon orc

*Orc Shaman
-11 morannon orc

Overall: 750p, 36 mass, 6 might + ability. But im not sure if this set is wise. Enemies can easily archer the mobile group down for example. Advice?

Any ideas how to make this army list better?

Seems no-one has anything to say?

I like the thematic background of the army!

Yes, I agree: the dragon's warband is vulnerable to shooting. I would replace the dragon's "Fly" update with the "Tough Hide". Your army has few Might; you don't want a situation where you lose priority and your dragon gets swarmed. I would also replace the Wargs with something more durable, possibly with Morannon orcs (which would also increase your low numbers).
I am not particularly conversant with Mordor, so I apologize for not offering more elaborate suggestions.

I vote to keep the Dragon's wings: flying Monsters rule the table.

Your mobile units should be safe from arrows if tucked behind Morannon Shields until the fighting starts, then they will be useful for flanking. You'll have spears behind every shield, right?

Six Might should be helped by the Taskmaster...though keeping him in range of your Heroes-in-need is a pain. Consider converting something into Kardush to replace your Shaman: you'll still have Fury, plus a power punch and inexhaustible Will (though nearby Orcs will not be pleased...)