Could you post a couple of examples of your own lists please?
That 3rd phase army is interesting; I've rarely seen Tau without Piranha skimmers, and lack of scouts would have to be an issue for it. So is the fact the Supreme Commander is almost certainly off the table in an orca at the start.
Interesting to note it's long range firepower is good but not great. Railhead hammerheads are good vs Leman Russes, but in reality you match them for range, to hit values and both tanks save on 4s - in other words, LR are about as good as killing Railheads as vice versa.
The key for you might be to include some artillery to get the first hits in, and force him to come to you instead of waiting for you to trundle across the field.
Force the blue-faced Space Commies to commit, then massacre them.