1-Focus more on decision making than luck.
2-Modify the ranking system.
3-Modify the progression.
4-The randomness algo is not so random: make it public or make it random.
5-Don’t pay to win or assume it totally.
1: I have been playing this game for a while, and I enjoy it when I have time not only to strategies on my choices, but also when I have time to react to the other players. My most pleasant games were games where I was in the final against another player, and I managed to apply changes to my line up to counter his. It seems every season it doesn’t take long before a meta comes out, and games finish quickly between turn 8 to 12, when you get wrecked by this apparently “beyond lucky” player that has a line up of perfect all gold all synergetic cards (All the good cards for Huran, all gold, all 300-300) when you are still struggling to pick a class of card due to poor incompatible choices and rerolls. So, design better your upgrades, champs, and scaling to reflect that. I still don’t understand how players can achieve this kind of “luckiness” maybe they are just good, but that bring me to my next point.
2-Modify the ranking system to reflect skill and give point to level up accordingly. Right now, you basically just apply a +XP according to the position you finish the game. Here are some other parameters you should investigate:
A-Who are you match against: if you are playing against higher ranking, apply a bonus.
B-If you finish the game with a line up of all gold, all compatible, 300/300 cards earlier in the game, apply a bonus. A player that consistently has that kind of hand knows something that most of us don’t. Go make him play with his Challenger buddies (or with his cheater buddies, on his island 
).
C-How fast you win: if you win early in turns, get more XP.
D-Survival factor; the more players have been out and the longer they have been out should give you more XP.
E-Health/Shield comparison. If you finish the game with more health and shield, then bonus XP.
3-The progression should be reflected in brackets that tell you which % you are. Also, if you are going to do some “Plateau” where you can go back down, then do it all the way, don’t stop at 6000. Either do it at each 500, and add a status to it (Bronze, gold, etc) or don’t do it.
4-Clearly your random is not random 100%. With the actual trinkets, we can actually see and feel this. Now is there something else to know? Do the early buys affect what you will get later? Whats up with all that? If there is bias in your randomness, then make it public. Tell us the “rules” of this randomness. If not, make it random for reel. Again, for a player to get all legendary cards, of a single class, all working together and this early as turn 10, there must be a trick to know. If you tell me that the “external aids” (like card counting software’s) are the trick, then provide one with the game.
5-Everybody argues that having a pick of 2 champs VS 4 doesn’t do a difference. But clearly it does. Charging 20$ to unlock this feature is basically saying: Pay to get more chances to win. You don’t agree, you don’t think that 20$ to get this feature is pay to win? Or you think that “Hey, game publishers have to make money in SOME ways…” then here is my suggestion:
A-20$ = what your offer now (4 champs instead of 2 + Skins and other)
B-40$ = 4 champs + 1 free reroll champs at start
C-60$ = 4 champs + 1 free reroll + choose 4 fav champs in your collection and get one of the 4 for sure at champ select
D-80 = same as C but add a “choose your minion type” before the game, so that you can choose witch of the 5 types that are available you want to have a 25% chance of rolling more then the others.
I also ask myself: since you get 20$ when players pay the season pass to get 4 choices of champ instead of 2, what prevents you from not giving good choices to players who don’t pay to frustrate them into buying the upgrade?
There you go. If you didn’t get the irony in the last point… what can I say.