With vague descriptions of the skills now available from oxm, I thought I'd dissect them to see what we'll be working with. Of course no morphs are shown yet, nor are passives.

Ice tree:

Polar wind: damages enemies and heals allies. I'm guessing this is some kind of aoe, as heals usually aren't targetable. Probably exactly like that spell npcs use that sends out a whirling ice ball along a path.

Ice fortress: the description said this gives you a defense boost. I'm guessing it will work like the npc ice wall, stationary and absorbs attacks from the front until the wall is shattered. Basically a damage shield that you have to stay behind.

Impaling sharfs: sounds like this will work in the same manner as Fiery grip for dks, pulling targets to you. It's possible that one of the morphs might knock back the enemy instead, which would be preferable for non tanking players.

Crystallized shield: also described as a spell to boost your defenses. It may be a damage shield, but I'd bet more on something that provides major ward and other defensive buffs.

Sleet storm: the ice ultimate, and likely the big explosion ability we saw in the trailer. That didn't look like a persistent / damage over time ability, so I'm going to guess it does one big burst of damage to enemies around you. Also protects allies in some way, either through a damage shield a la magma shell or through some kind of buff.


Nature tree:

Fungal growth: seems like a basic cone aoe heal, like combat prayer, nothing special.

Healing seed: description says you plant a seed that heals nearby allies over time, meaning it will probably be a stationary effect like blood altar.

Living vines: seeks out and heals the lowest hp player. At first glance this looks like a burst heal like the templars breath of light, but it could also be a heal over time that "sticks with" whichever player is lowest on health, moving between players until the duration is up. Makes more sense as a living vine to me.

Green lotus: a damage buff. We don't know if this boosts the party or just the warden, and we don't know if it's a totem style static effect or if it travels with the group. Chances are it will provide major sorcery. I'm hoping that one of the morphs will also provide major brutality (giving both buffs like Molten armaments would work well for Hybrids), and that the other Morph will also provide major mending to help healers

Nature's grasp: teleports you to an ally. Outside of pvp and the rare tanking mishap, I can't see this ever being useful. The morphs could make or break this ability.

Secluded Grove: the nature ultimate, slowly grows trees that heal allies inside the radius. My guess is this will be a channeled heal like the templars, but it would Definitely be unique if the trees blocked line of sight for ranged attackers.

Animal tree:

Cliff racer: the direct damage spammable for the class, calls a cliff racer to dive bomb your target. My guess is that one of the morphs might change this into a lingering damage over time effect, where the bird hangs around and continually pecks the target.

Subterranean assault: an underground creature moves away from you in a straight line and stuns and damages enemies in the path. Doesn't sound all that useful to me, except possibly for control of groups as a tank.

Growing swarm: sends BEES! to assault your target, dealing damage over time. I was really hoping for an insect swarm, glad we got one. Morph possibilities could include having the swarm spread to other nearby enemies, or even spawning a short lived Wasp when enemies die to help you fight on, like those sometimes spawned in pve after fighting wasps.

Bull netch: Simmons a netch that restores your stamina over time. Morphs might include changing this to a magicka restore, or having it effect group members as well.

Bird of prey: this one is interesting. It's listed as a speed buff, probably in the form of major expedition, but I'm curious if it actually transforms you into a bird temporarily. Could be fun.

Wild guardian: the permapet bear ultimate. We know that one morph for this causes the bear to auto revive itself if it dies, rather than you having to resummon it. That, to be, sounds more like the tanking morph. The other morph will probably give the pet more damage. Hopefully we'll have some way to customize this pet, allowing for a wolf or senche instead of a bear, purely visual of course.
It's important to note that, being an ultimate, this pet will scale no matter if you're magicka or stamina based, so it will be useful for all builds.
It was also mentioned that the pet will have new ways to control it, so we may see a new pet interface for both wardens and sorcerers.