First off, Tau army is a heavy shooty army. Its either going to be a move around and shoot and or a sit somewhat and blast away. 1850 you have very very low model count. If this is because its all you have, then you will have just wait till you get other units. From my understanding thou, you have other units to play with.
Deep striking is tuff, you dont know when you are going to get your units in and that is the key. Putting all of his army vs very little of your army and hoping that you can get what you want in on time. Scouts are going to die fast via shooting from Tau. Bikes are going to take a lot of ranged damage because they are the only other unit on the board. Next you have to roll well to get your termies in. If you do not roll well, you are going to see a unit at a time teley n only to see it die.
I would drop two units of termies, pref hth units and add in four units of tactical marines. Maybe two units of five with two heavy bolter in each unit for dev units. You just need some ranged dps and some bodies on the board. Termies are more less best used when you need them. Having to many could cost you the game because you are waiting for them to tele down. Then again, it does not take much to smoooh down a five man unit of termies.
6x tact units with a lascannon in each unit is a big waste of points. That is going to give you six shoots a turn and the rest of the unit is just going to be a waste of points.
You need to be moving down the boards and get in to hth with basic tactical marines if you can. I will be reading up on the DA codex so I cant really give you a idea of what you might need. I just know that many termies is a point sink and will die with ap and mass flash light fire.