Howdy! A few comments on your list:
I'm not going to offer opinions on your choice of units or the combination of which units work better with other units, but there is one theme that must ring constant through every Ork army:
*********Use Mob Rule****************
Orks have awful leadership; as bad as Tau. They get around this by running around in huge mobs of boyz who are fearless in numbers. By having so few models in each squad, you're stamping an invitation on your army for your opponent to make you run away.
As a Tau player, you know what I would do against this list? I'd split fire among my various units to kill a couple of your Lootas, a couple boyz in each squad, and work on down the line. Then my Sniper teams would each get a squad, and my pathfinders with their 3 target locked Rail Rifles would each target 3 more squads separately, and you'd be sitting on 9 pinning tests from non-fearless units, with a base leadership of 7.
If you're going to play Orks, you've sorta gotta follow one of two principles:
1. Da bestest Orkz haz da mostest orkz - IE, you make a green tide; full units of 15 Lootas, 30 Boyz, or whatever combination you like.
2. Deze trukks iz makin' me teef rattle! - IE, you focus on speed in your army, and while you don't have large units, they have some amount of protection from being inside a vehicle for at least a turn or two.
Personally, I tend towards the latter - a typical 1850 list for me includes Ghazghkull Thraka + 10 uniquely equipped Nobs in a Battlewagon, followed by as many trukks full of boyz as I can fit. My opponent now has two choices: Try killing the Battlewagon and slowing down Ghazghkull (because he will eat your entire army by himself) in which case the rest of my army screams into combat and destroys everything, or focus on my other trukks, in which case Ghazhkull and the nobs get into combat and multi-assault as much as they possibly can.
If you want to have a shooty army (Lootas) then take 3 full squads of Lootas, attach 2 Big Meks with Shokk attack guns, and stick them in cover. Or screen them with Gretchin. Tack on a couple of battlewagons for fire support, and as many shoota boyz as you can afford. You end up with a gunline that can outshoot a Tau gunline; those Lootas are getting 15-45 shots per squad per turn - its downright nasty.
The one thing you really CANNOT do is do it all at once. Orks are very, VERY versatile - you can make an effective army out of them to follow any kind of doctrine; speed, Dakka, mob, Sneaky, outflanking, superunits....but you can't do them all at once.