I guess, we have similar mentalities, playing this game. I don’t complain OP on any troop or weapon too. I understand that someone may feel that way though. In Bracket 1 of GW, any weapon used in defense or offense seems “OP”. 
Dagger of Zaejin is not of same significance compared to other weapons costing 75 diamonds. Wouldn’t you say?
Don’t mention about dagger of zaejin. 
it is OP making me win in B1 GW.
Hehe…Don’t take the term OP here. 
Well, I agree rope dart is overpowered (relative to other 14 mana weapons) and needs a nerf.
But I don’t see an extra turn as a problem.
Reducing armor to 0 could go or mana cost should be increased to 18 (like Life and Death).
All extra turns, on weapons or troops, are OP to a degree, since the extra turn is the engine behind “1-turn” wins. And it’s often a matter of pure luck whether you manage to escape a lock/loop or not.
But if we start nerfing on that basis, we also have to remove all the gem converters, since, used properly, they should give you a 4-match and hence an extra turn. And, no surprise, the empowered ones are some of the most widely used troops in the game.
The extra turn, whether it’s on a quick weapon, or a goblin, or beetrix (even when not guaranteed), or mistralus, etc, or result of calculated gem conversion, is the core of so many popular team builds.
Start nerfing… and where does it end?
If you just nerf one weapon, though, you’ve just made all the other extra-turners that much more powerful.
Nerfing should be reserved for game breaking stuff. And rope dart isn’t game breaking, by a long shot.