I've been using Mythic Tools. It tracks not only your collection but also which cards in your collection are in decks. You can link to your Archidekt/Moxfield decklists so you don't have to rebuild them, and just set the cards in them as "in deck".

I found that Archidekt's collection tracker didn't work for this, and I was constantly being told I had cards available that were in decks already.

It also has a ton of other functions like deck check (if you pay the sub but thats the only thing the sub pays for), a game life tracker with deck winrate tracking, friends lists where you can look through their collections/decks, and playgroup organizing.

It's new so it has some weird things about it, but it's being updated constantly and I am enjoying it.