Agree that Battlewagons have been made really strong in general, I think that an increase to cp and trample deceleration would be fine. I have no issues with their current armor values.
Everybody keeps on mentioning the speed of the elves, but if we are talking about the specific matchup vs dwarves you seem to be forgetting something extremely important about the dwarves: the tunnel system.
How can you possibly argue that you can outflank and harass the dwarves when they can teleport troops instantly to whatever you are trying to harass? 1v1 Lorien Swordsmen lose to Iron Hills Guardians, which means that if you split your troops up to harass external settlements you are sentencing them to death against a skilled dwarf player. I think Haman nailed every other point on the head except this one.
This is one of the prime issues in this matchup, besides the fact that Iron Hills can just spam you with guardians with tower shields and win. The protection that dwarves have through the tunnel system is currently unmatched, and makes harassment almost impossible unless you use large groups of troops, in which time the dwarves can easily move forward and harass your own farms, which don't have the ability to have troops teleported to them.
EDIT: I just thought I would draw some correlations for those of you who don't think that the battalewagon trample is too strong. So lets compare, If we look at other factions basic cavalry we have Gondor Knights at 700, 120 command point cost, who get stuck after trampling half a battalion of orcs, and the multitude of different cavalry Rohan has, who cost 400(I think, I always get them fully discounted at 280) and 90 command points, and have the same trampling power as Gondor Knights.
Compare this to the battlewagon, with a default cost of 600 and 20 command points. The resource cost is ok, command points are pretty low. Then we look at the trample, a battlewagon can easily kill a battalion of orcs without slowing down, and can throw powerful explosive casks which by themselves can wipe out clumped infantry. On top of this the battlewagon can be provided with leadership and healing capacities, all for 25 command points. Now, if anybody wants to argue that is not over-performing for 25 command points, you are either biased or a fool, no offence of course
So, to wrap it up, I just think that Battlewagons need a command point cost increase to at least 60, preferably 90, and an increase to trample deceleration, to be just above normal cavalry in their trample strength, say able to trample 1 full battalion of orcs or troop equivalent before slowing down. I think the armor buff was sorely needed, but giving them a straight armor buff without nerfing some other aspects made them a little bit overpowered. Food for thought