8th edition has made the big beasties incredibly stronger but are they really that strong and cost effective?
On their own they are but if you put them in a bigger perspective they are not. A block (3-6) of minotaurs or trolls is great to kill a war machine or some cavalry but against a unit of 30 infantry their chances decrease enormously. They still can shred them but steadfast and at least 10 attacks (probably more) will make a bigger comb.res. and since big beasties don’t have the best LD (4 for trolls) they will run away easily and then you have 200+ points in a position where you don’t want it.
Therefore you want to pair your units of monstrous infantry or cavalry with a nice and sturdy block of infantry. As example I will take the Khorne Deamons army of the studio. In the last battle report against the High Elves the Bloodcrushers didn’t get back their points value at all, that’s because Shawn rushed them forwards (which is almost never a smart move), you should keep you battleline a line as much as possible and then in the same turn storm forward. In the Deamons army you should charge with the Bloodletters in front and hit with some monstrous cav. in the sides (not to break ranks just to have more comb.res.). This will mean that you got 2 charges, 1 flank, some ranks and 1 or 2 banners. That means a static combat res. of 5+ and a lot of attacks (and stomp attacks) left to increase it and break your opponent, once that is done the monstrous inf. or cav. probably has a higher movement and is likely to catch your opponent. Meaning you got your victory points.
This is of course not fail proof, you could miss your charge or lose the combat, if that happens your opponent still has to make a choice, does he charge the monsters or the infantry, either way he is getting the one or the latter in the flank next turn. And that is what it’s all about, being sure of your own actions and letting your opponent make a choice with the dilemmas you put forward.