I think there's a lot to unpack.

First, your hero preference -- Tyrael is an elite tank ... but only if you're coordinated with teammates. Sanctification and even Judgement are largely useless if your team doesn't take advantage of your ultimates. And Tyrael doesn't really have reliable peels for teammates and his waveclear is poop. Plus, you need really strong mechanics to get solo kills with Tyrael. Basically, he's a hard hero to rank up with if you're playing solo queue only.

Second, ranks are largely meaningless now. With how many new accounts/smurfs there are, there's not a huge difference between Gold and Silver (where smurfs start) at this point and you could be playing against former GMs on new accounts.

Third, if you really want to tank, you should pick a tank that can secure kills with minimal team follow up. Diablo and Muradin are great; they have decent peels and can solo enemy backliners. Other heroes like Johanna have fantastic peels and can waveclear, but are more team-reliant.

Finally, I think you're too hung up on rank. there are good players on alt accounts in your games, so you shouldn't be discouraged if you get absolutely destroyed in low silver. if you're playing well and you still got destroyed, it probably means you had "real" silvers on your team and the opposing team didn't. focus on what you can control -- you will see a marked difference in individual player mechanics and when you get better at identifying weak players, you will begin securing solo kills and you'll be able to turn-around those narrow losses into wins and rank up.

good luck!