Don't try going toe to toe with battlecruisers and tanks... you'll lose. Instead, rely on the other weapons that protoss gets. Combating battle cruisers can be pretty easy. A couple of templars with storm can really hurt battlecruisers and send your opponent into a frenzy. Also, arbiter's freeze really will kill them, not only because you put him at a disadvantage for a minute, for you will also kill his number keys (ctrl+1, ect.) so he won't beable to group up his ships and he will prob retreat. Also, scouts will pretty easily own battle cruisers if you have enough of them. Even 12 scouts VS 12 BC's would cause some serious damage to the battle cruisers. As far as tanks go, if the opponent is going all tanks, you need to hit them with air. But, there is another strategy i've done before. A standard defense tactic by terran is to put 3 supply depos infront of some bunkers with marines, then put tanks behind the bunkers and maybe add a few turrets. There are two ways to combat this. One is to make a few zealots, get armor and speed on them and take about 8 of them and run right up to the spply depos. The tanks shock will kill the supply depos and your opponet will be hurting. However, my favorite strategy is to group up about 12 zealots (they dont need to be upgraded) then get an arbiter and send him in above the tanks. You'll probably need to sacrvice the arbiter for this. While you're above, recall the zealots and they will cause major mayham. The tanks will probably end up killing each other. Anyways, the #1 thing you should be using is arbiter's freeze... heck, you could even just go over and freeze all his tanks, then rush him with guys....