Dreads arent really a problem (IMO). They're only high resist is physical. They have (At max, 650, which is extremely rare) 550ish hps, and a flamestrike does 50-120 on them. (Again, most having 25-35 fire at most). Also, you can pretty much poison them every time, hence making the rider stuck on foot for a while. Also the fire breathe is HP dependant, so 1-2 flamestrikes, 1-2 special moves, that firebreath becomes a weee tiny fireball.
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Maybe a capping of the firebreath, but most peoples dreads dont have the HPs to do what most people propose anyways (35hps aka an AI, but if ur 70 fire, they dont usually do over that unless full health). OH! And you can paralyze them for 2-10 seconds without EO/Para, making them unridable and useless.
Again; just saying, the horses are easily beaten. (Again, all my opinion.)
I do agree however, the greater dragons need a nerf of some sort... But thats a story for a different thread =]