I think that 5th Edition wasn't very kind to Tau. The codex needs an update as TLOS makes it difficult for suits to hide properly and the wound allocation rules really minimazes the uses of an ethereal.
Pathfinders are great though. I suppose it would be a good idea to take 2 teams of 8 and equip 1-3 of them with a rail rifle. Markerlights are a must as always but much more effective now.
The new missions need a lot of mobility so mechanised is more effective than static (but that was always the case wasn't it).
Now about the stealth marker Drones. Do u think they are effective enough? I really want to use them but they have a very low BS. I'll try them though and see what the result is.