I think it's reasonable that elves would have access to a lot of different types of plant-based poisons. That in itself would give them a big advantage.
They might also have access to plants that would quickly heal even mortally wounded elves, and certainly fire-retardant saps are possible, and would be widely used in elven lands.
I totally disagree with the idea that they'd be able to make any plant-based material better than 75 (bronze in it's current form), but 75 isn't really *bad* when you can just grow whatever it is, and never have to worry about scarcity. 50 elves armed with bronze-equivalent gear, and curare-tipped arrows, is worth a lot more than 5 dwarfs armed with steel.
Heck, a shellalagh is a perfectly great weapon, especially if you can give one to the vast majority of your citizenry. And Elves might have things like "longbow plants", "sword bushes", and the like.
Elves aren't really about numbers though, as Granite26 pointed out. Elves are a defensive race, in that aspect not entirely unlike dwarfs. Elves know their lands: they know how to defend them, how to hide in them, and how to fully utilize every single resource contained within their environment. They're just a lot more mobile, and a lot less durable, than dwarfs.
Elven armour would likely be laughable compared to masterwork dwarf steel plate in terms of sheer durability, but it would probably be very light and flexible, and might give bonus resistances to missle weapons, offer great camoflage, and provide some resistance against special damage types, like fire, acid, lightning, and cold. It'd also be a lot more quiet, and again, a lot more generally available, than plate.
Elves, I think, should generally fight mostly as guerillas. They could bushwhack, ambush, lay traps, do a lot of sniping, and try to divide their enemies up.
And I agree about their skills. All the adult elves that exist at the beginning of the game could get atleast one random Legendary skill, to represent the sheer weight of years they've got on everybody.