I've only played for 10 days yet and haven't even gotten my first 6* yet, so this will be my first impressions of the game (and Plarium).
Reading the posts above, I get that many players are frustrated with the RNG nature of the game and the artifact unequip costs that I too found puzzling first (more on this below). However, I come to this game with zero sense of entitlement and very low expectations, having paid nothing for it - nor will I ever. I'm basically an eternal parasite off of Plarium's free (for me) work - I'm not stuck with them, they are stuck with me. I start the game fully aware every time that I'm gazing into Plarium's money making abyss that employs the best techniques to stir feelings in me that will hopefully make me want to part with my money. So from this perspective, I don't really care if it's "unfair" for f2p players, I only care if I'm having a good time or not, and if I'm not then I'll go play something else. So far I am - I like the game, especially its potential for automization, beating AI and finding good synergies. The good graphics help too.
Hence, I won't critique any aspect of the game that is obviously designed to make Plarium money - I expect the game to be as packed with such features as is possible without losing too much of a player base that might be willing to part with some money. If not, Plarium is a worse min/maxer than I am, in which case more power to me, right?
One matter of game design I just find confusing though, with no clear benefit for Plarium or its players: Why is the artifact system such a mess? You have set bonuses that overlap with main stats. Not to mention the added complexity of rarities and substats. Here's what I'd do: Away with all set bonuses that enhance stats. All sets come in 3 pieces, not 2 or 4, and all of them add a special feature such as lifedrain or retaliation when you complete the 3-set (hence 2 such abilities are available per champion). There are no flat main stats, only scaling percentages even on first row equipment - all free to combine. All substats are instead flat, and come as perks with +4/8/12/16 like they do now. Remove rarities entirely - stars is the only defining property of rarity and drop rate, along with the actual set effect with more powerful effects already being more limited. Limit upgrade potential based on stars so noobs won't overupgrade shitty equipment that they will want to swap out in a few more days of playing - I promise it will be good even for monetization purposes, since new players will then be better to hook on the game than using this overly complex system you have now.
As for the cost to disequip, as it is now, I think it's almost always a mistake to pay it. Better to destroy the equipment if it is outdated. If it's outdated on one character, it will soon be outdated on another too and you're better off investing that silver in upgrading new, better equipment. If you have like a 5* +16 piece that is so good as to merit that upgrade, why would you want to remove it? The only time I think it might be worth it is if you have some awesome equipment and want to permanently repurpose a champion for something completely different, such as clan boss. But before doing that, consider if you can't just make a new champion for this purpose instead and use the equipment on him instead. Perhaps it would be better if unequipping was simply impossible - scrapping was the only option. As it is now, Plarium invites noobs that have an emotional attachment to an equipment piece to part with their in game silver, so as to make the in-game currency more scarce and encourage replacing it with real money. It's a trap though.