Almost anything can be used if you're good enough (or your enemies are bad enough). If you enjoy Blitzcrank top and that motivates you to play more games, then you might be better off playing him.
But, let's be real, he's not a great top laner. It's pretty much his worst lane, since he would face the kind of champions that want to be on your face, as opposed to most mid laners or bot laners, who tend to prefer being at a distance.
Try him a couple more games in normal before going ranked with him. My preferred way to know if a champion is worth playing in ranked is seeing how it does in a game where you lose lane, so I guess play until you lose the early/mid game and see if it's your type of playstyle. And even if it doesn't become a regular pick, you might want to have him considered as a counterpick against some champions (some adcs like Lucian, Quinn, Vayne tend to appear in the top lane from time to time).
I believe that you must play whatever you like and whatever you are good with. If you like Blitzcrank top then play it, if you are good you will win. Sure, Blitzcrank top will be hardest to play than Darius but that's not a problem. Play whatever you want!
Pretty sure Blitzcrank top will be viable in your elo range since most people don't really know what they're doing so you can get away with it. Once you climb to higher elos like gold for example, then no, it will definitely not be a viable pick.
But, let's be real, he's not a great top laner. It's pretty much his worst lane, since he would face the kind of champions that want to be on your face, as opposed to most mid laners or bot laners, who tend to prefer being at a distance.
Try him a couple more games in normal before going ranked with him. My preferred way to know if a champion is worth playing in ranked is seeing how it does in a game where you lose lane, so I guess play until you lose the early/mid game and see if it's your type of playstyle. And even if it doesn't become a regular pick, you might want to have him considered as a counterpick against some champions (some adcs like Lucian, Quinn, Vayne tend to appear in the top lane from time to time).