depends-i use it for hacking as he was running off due to lack of respect for me. i tried everything including leading inhand,feeding less,riding more,hacking more,hacking less,hacking alone,hacking in groups,hacking with quiet horses,hacking only after schooling (thinking he might not do it if tired) hacking before schooling (thinking he might not be in such a hurry to get back) turning circles,walking all the way,trotting all the way,lots of transitions,shoulder in,leg yielding, and not a single one of these worked!this was over a 2 year period-then i resigned to a dutch gag. he's normally in a snaffle so i just put it on the ring below this. i have 1 set of reins on the snaffle for normal transitions and one on the gag reins for emergencys-after putting it on i used the gag rein 3 times over 2 hacks and he's not even attempted to run off since!

so in short my answer would be it depends-if the horse is strong all the time then no-i'd recommend lots of schooling and basic work to stop them being strong-but if the horse is strong in 1 situation and all other avenues have been explored then i dont see a problem with it!

I use a dutch gag for showjmping and ross country i wouldnt say i need it badly cross country i just have it there because my horse gets a bit strong sometimes If you have only just started riding or are heavy handed i would not recommend it a it is quite a severe bit

Just to add, you could always try a bitless bridle, a bosal or hackamore for example.. These can be just as severe as a harsh bit, even worse in the wrong hands (they apply pressure to the poll and delicate nasal bones, so the reins are only used when an aid needs to be given, you don't need a contact like with bits), but for some people can solve the problem as the horse doesn't have anything to lean against.