I think the fleet you mentioned is strong but not unbeatable.
It is a bit luck dependent as well with many bombers and many leadership rolls. I still think a Chaos fleet with several 3 turret ships for example has good chances (i dont know why they suck in tournaments, maybe chaos players play too chaotic :-D ) they could stay at a distance using their lances while beeing able to defend themselves with high turret values and some fighters (even close ranged batteries could take on incoming ordnance if the tau doesnt close in.
Orcas shouldnt be too hard to destroy with AC (even taus fighters cant be everywhere). The fleet also has the problem that it has to stick together. The two heroes alone cant take enough fire.
After all its theory and each game is a bit different.
I had a lot of games with tau sometimes they own and sometimes your bombers just dont do anything. Especially vs a high turret chaos fleet i had problems, vs orcs i almost always won (low turrets...).