From a Fish point of view... of course.
Tinker must be handled as usual
So there is Gush and Preordain
Then we have Lodestone Golem and Tangle Wire
We have Bazaar and Bridge from Below
The occasional Oath
And the mirror
I will put cards out there and discuss the role of these card per archetype:
Trygon Predator:
According to the newest results this guy is the answer against those aggro shop builds because they are well prepared against Ancient Grudge. But what about those new Welder/Misstep/Workshop builds? Turn 1 Welder might cause serious havoc. Then again Trygon is not the card that should deal with Welders in specific. It is the card that simply cleans the battlefield. When answering Welder, keep in mind that they might run Mental Missteps.
Phyrexian Revoker :
This is a 2 mana answer to Welder, but be aware that they could remove it with Barbarian Ring and/or Triskelon. Ok, enough about Welder, Phyrexian Revoker has been an important tempo card to gain mana advantage. So if you are running Wastelands and Noble Hierarch, running Revokers is a good plan. Revoker can also be an out in tight spots naming TV, JaceTMS, Triskelon or Grim Lavamancer. It is not as controlling as Null Rod and never will be, but it has more flexibility and legs. It hits the tempo game on 2 fronts, mana and clock. I am not sure if my next design will pack these cards, do I want flexibility now that I know the meta better?
Gaddock Teeg:
Ok sure, it hits Gush, Jace and Tendrils. But we saw that those Gush/Bob decks with Tinker as the main win condition don't run Tendrils or Jace. So I am not really sure about Gaddock right now. On the other hand, Smokestack and Dread Return are not to be underestimated. So against blue Gaddock Teeg would hit Force and Gush, which is pretty important if you can back it up with good support. And in other match ups it hits the win big win conditions. Seems a bit too far stretched, but it is still a close call for me every time I want to design a fish deck, which is a meta deck. Besides hitting smokestack and dread return is not going to cut it in those match ups.
Ethersworn Canonist:
I like him now. Seems like the only card that would slow down Gush.deck so they can't do all sorts of drawing, gushing and tutoring in one turn. He is dead in the Workshop match up, but that is just it, I am not looking for highly flexible cards now, I want specific answers again. I think Canonist would go well in a deck that packs full set of Trygon and additional Workshop answers. Just accept the fact that Canonist is going to be at best a chump blocker against Panter or Golem. Just side them out for Kataki and your all fine.
Goblin Welder:
Welder was my Tinker answer before Inkwell was printed. But now, Inkwell is simply replaced by Blightsteel. I like how 1 drops in a deck answer Tinker. Right from the start you are saying to your opponent, you better have Time walk next to that Tinker or have another way of winning. Sure, it can be played around but it does add up to the pressure and the follow turns you will cast things like Canonist which happens to be an artifact and works well with Welder. But more importantly, it is another card hampering with their plans. Digging for answers is slowed down and so on. Welder is also a great tool to mess up with Workshop. I like how welder hits Blue and Brown. It becomes interesting with cards like skullclamp, moxes, gorilla shaman and so on because then, it acts as a card advantage engine. I have always liked how Mishra's Factory plus Welder in play could get back Ethersworn Canonist from the grave and play around things like Hurkyl's Recall and Rebuild. It is hard to find a better 1 drop that does so much for the Fish player. It cuts off win conditions for a pesky

. Usually the stuff that does these things are 2 mana bears like Gaddock Teeg, Meddling Mage, Leonin Relic-Warder... Be advised though, according to Steve, Brian will soon have a solutions for the rise of Welders/Missteps. Maybe he will just run Welders and Misstep himself? Slaver?
Qasali Pridemage:
The card still amazes me. It has a triggered ability and an activated ability that are relevant. Nevertheless, there are times that he just doesn't cut it. Maybe it is because of the tempo you need to get him online? And you do have to sacrifice him to nail a Lodestone Golem or Smokestack. Pridemage is good, especially when you could build up the mana those early turns against shop. But then again, I would rather cast Trygon Predator or Kataki, War's Wage to really hit their board. Pridemage does have pro's against TV but some people are cutting that win condition nowadays for bad or good reasons, we don't care. I would rather target the spells that find TV. And who knows maybe you can use Welder given they got an BL or LP in their grave. Or you could just run Gorilla Shaman... Qasali Pridemage seems too over-extensive in the light of our Welder/Trygon plan. I am not even talking about the colour issues. For me Qasali is like Gaddock Teeg, he hits some cards here and there in more than one match up, but he doesn't really put it up their but.
I suggest that you also just name a card and share your thoughts about it in a similar way. You can discuss a card that is already discussed by me. The main question is "what will it do against the meta"? I will write more later on other cards or add to the ones already here.