From the way I see it, there are several angles towards the problem:
1. The issue of long queue times
Okay, I think it's pretty safe to say that everyone wants shorter queue times. Long queues mean long periods doing nothing, earning nothing etc. unless you have something else to occupy your time with. The queues can be attributed to what appears to be a small playerbase, and possibly the matchmaking algorithm.
After a long queue, it's understandable if a player finds it frustrating to have their long-anticipated game cut short by an insta-concede. In my opinion, it's the lost time, rather than the lost rewards (IP/XP from the game) that hurts more. That time spent waiting is essentially wasted, because what you ended up with isn't a game that is satisfying.
2. The issue of bad matchups
I think when you go into matchmaking, you have taken a risk to be put up against any and all kinds of decks. It's a rare deck indeed that will have even matchups against all others, and so there is the possibility of 'hard counter' matchups. Ideally, a solution would be to play around with the balance so that there is a little counterplay between even extremely advantaged decks, although a player's deckbuilding skill can contribute to how much the 'imbalanced' matchup affects the deck.
3. The (perception of) player attitude
To be honest, it's quite subjective to determine the attitude of a player based on whether they insta-concede or concede later in the game or never concede. The argument for selfishness does cut both ways. Is a player selfish for wanting to keep the game going when the other player doesn't? Is the other player selfish for denying the other player the chance of a match, especially after waiting in the queue?
I think it's a little presumptuous to put a blanket statement like "insta-conceders are selfish" and leave it as that. A player who just waits the full time out and doesn't play anything can be pretty darn selfish too. I mean, if I wanted to play that kind of matchup I would have played Puffy instead, and at least the goldfish doesn't waste my time in game.
4. A solution?
What I was thinking of is to emulate something like DOTA 2's matchmaking system. I'm primarily thinking of the 'high priority' queue. If a player fails to load into the match, all players are put into the high priority queue, and are assigned matches preferentially to others. In the case of IW, the person conceded upon quickly (say within turn 1-2) would be put into the high priority queue while the other would join normal queue.
My thinking goes like this. As a player being conceded upon, you want a game. The system gets you a game fast so you don't have to wait 20+ minutes to play another person. So, instead of saying "Ah, damn. Another half-hour queue" it's going to be "Oh, you don't like my deck? Never mind, I can play with someone who's more sporting".
As for the insta-conceder, either a matchmaking delay or a low priority slot in the queue might be appropriate. I've been on the receiving end of my share of disadvantageous matchups, and naturally I don't win those often. However, to give up without trying is, in my opinion, not something to be encouraged. If after a few turns your plan, backup plan, and desperation options are exhausted, fine, I understand, you tried. To go "Ah, puffy this. I'm not even going to try", especially if it comes as a cost to the other player, is not something that I can agree with.
Regarding the issue of 'tryhards' and deck testing in the normal queue, I honestly don't know. There are multiple sides, from players wanting to test decks before ranked, and for those who want to feel good by taking strong decks and stomping others. I suppose it largely depends on your perspective of what you want, but personally, I'll just take the matchup. Even if I'm playing Uncontrolled Rifts vs a triple Verore oblivion deck, I'll play it out. It's a player's right to play a strong deck, and I don't think it's fair to put a limit on how 'strong' a deck can be to be banned from normal.