ok, first, i'm a lancer myself, and a horse breeder.
So, the dev try to fix the cavalry advantage, because yes, there is one. So rp player our realistic people could say, hey it's normal, it was like this in the past. Yeah, but how many time it took to breed a horse? you could not get that many horse per day, and I think it's a major problem for now.
there is no use to nerf their maximum hp, because there is hundred of horses that wait to take their place and die. i'm in a small guild, we really have just a few stable, but I have more than 2 cart full of hardy, and it's way more than what we can use, way more. not a surprise that some bigger guild dont care to lose hardy during jh, not a big thing for them. Then, we can make an infinite amount of hardy, just by training again a simple warhorse, so a 100% chance to get the third tier horse. honestly, spirited are not a big thing to.
So, even if you nerf stamina, health, or even cut speed by 2, it will change nothing. what can make lancer a bit op for now, is because they dont care of their horse. We all go with 2 or 3 hardy in IB, and dont care at all if we lose them, in a small guild. what about guild that have 5 large stable.....
so yeah, the suggestion is there. First, lower the breed of horse, maybe 35% less. I would thing of 50, but pretty sure people would say no. then, it's good that the warhorse are 100% rate. but the way we get hardy should change. it should be a % of chance, so chance matter now, and ONLY if the horse trainer have the right level, and the horse warhorse would be of 50 quality or better. same with spirited, with a pretty lower chance. it should correct most of the OP stuff of lancer, since now they will care of horses. it's pointless to have this many of horse, and kill some to have leather, because you have way to many.
to balance thing, horse breeder should get a light xp increase, since they will be able to train less horses this way