I know it was terrible in EA (so.. so.. terrible) but wondering if anybody has progressed further to tell me if it gets good later on? 1 shot wood totems and an incarnate that is worse than the black cat you get for free.

Personally, I think summoning is great, but I thought it was great in the EA too.
They buffed the incarnate to become a super incarnate at 10 points, which is cool, but I haven't gotten to 10 yet to test it.
They also granted all incarnates a Taunt ability, which forces enemies to target them for a turn.

The trick in my opinion, is to invest heavily in the Summoning skill and make good uses of the 2 Infusion abilities on the incarnate.
Summoning improves their dmg, health, and all received armors by a whopping 10% per point, and the infusions grant a large amount of additional armors and a +25% damage increase for each one (this is unlisted in the ability description but shown on the tooltip for the buff).
The summon becomes quite durable and deals good damage, especially with their opportunity attacks.

I have been playing Summoner on Tactician and have felt very good about the performance of the abilities and the playstyle.

The flexibility to change their damage type to match the enemy is part of their Strength.
If you have the opportunity to prepare for a fight by Summoning and Infusing before the battle you will get a lot of extra mileage from the class as well.

Summoning also has great pairing with a skilled Hydro/Geo party member. The Summoning bonus to received armors synergizes with the extra armours granted from Hydro/Geo passives. The combination makes for an Incarnate that is hard to kill, but still easy to replace.

I tend to prefer the Blood Totems and Incarnates. The Blood Totems have a significant bonus to health over other totems, and the Incarnates gain a single-target physical nuke that also heals them, resulting in even greater survivability for both.

Edit:
I got a chance to try out the Incarnate Champion, at 10 points of Summoning, and it is very strong. I noticed a large health increase and a slight boost to damage as well. Plus they look damn cool.

I also tested out Supercharge, and it's still crap. The 50% increase to damage is additive with the bonus from Soul Bond, their Finesse, and also their One Handed skill.
Ultimately it means you waste a memory slot and AP to get a fairly small overall damage bonus and kill your summon the next turn.

Does this also apply to summons from other trees ? like if I add points in summoning will summons from other trees such as Raise Bone Widow get these benefits ? and does totems count as a summon as well ?

The fireball incarnate is literally a combination of the fireball spell and a fire elemental, it's to bad he doesn't heal from fire damage.... lol. Enemies won't target totems very much as long as you don't group them up so it's not really to hard to have a couple totems and an incarnate laying down damage every round. Of my 4 characters my summoner is definitely pulling her weight.

Yes it does!
When you summon from another tree you will still be able to see the "Soul Bond" buff increasing it.

Yes, they all get the buff soulbound as far as I could test it so far, so the blob of Necromancy.

That kind of means, Ifan must be a Summoner though.

True, but they do have 100% resistance to their own element. You can position the Incarnate next to several enemies to enable Opportunity hits and still cast Fireball at its feat to hit them all w/o any drawback.
Also if you buff them with more resistance (e.g a party member with the Leadership passive) then they will gain more than 100% resistance and will then heal proportionally from their own element too, thus adding healing to the previous scenario.

Do you know offhand if they changed Dimensional Bolt to be 1 AP?

It's 2 AP.

I don't understand this. Do you mean to say the same character must have Summoner and Hydro/Geo?

Summoner is also really good with necromancer summons cause it buffs them too; my bone widow at level 12 has 2500 hp and does 250 damage :O

Yeah the only really negative thing is that basically every summon other than elemental totem erases existing summons. You can never have a personal army, and even if you can summon a condor, a cat, an incarnate, the bone widow, the bloated corpse, and more, you can only have one of those at a time. Which since the Incarnate at high summoning levels becomes absurdly powerful in practice renders all the rest of those obsolete, which is a real shame. Not sure why they designed it like that. You can get elemental totems aplenty (woohoo) but 1 summon and some totems is certainly not my favorite summoner ever from any game, let's put it that way. Not saying they're not competitive, I'd just love "moar summons" personally. I know, I know, balance and all that jazz, doesn't mean I have to be happy about it.

The same player doesn't have to, but it would improve the armor granted from Infusion abilities.

If the Summoner has points in Hydro/Geo then Farsight/Power Infusions grant more armor, respectively.

If any party member casts Fortify or Frost Armor on a Summon with Soul Bond then it will also grant more Amour than listed by the ability tootlip (due to Soul Bond).
E.g. if the Summoner has 10 points in Summoning then any cast of Fortify on their summon (even by other party members) will grant double as much armor as listed.
If the caster of Foritfy has high Geomancy already then the Geo passive improves their amount, then Soul Bond improves it again, for a ludicrous amount of armor.