Yeah but you just made it vastly harder than in 2E.
You made it two checks - double the fail chance, and the fail chance is high - AND you then put disadvantage on the attack, which is at the very least equal to the -4. And what did you give them? One normal damage attack? Where in 2E you could hand out whatever.
This is why 3E was the biggest disaster in D&D history with regards to "trying to do cool stuff", because it had a rule for everything, and in practice that meant making like 3-4 checks (often with an additional -4 penalty for not having some Feat or another) to do something that in 2E was just an attack roll at -4.
This is also why 4E was pretty good at this, thanks to Page 42's table, and the associated text, where it directly encourages you to make checks to do cool stuff easy, not hard, and if it's stuff that'll happen like once a campaign, like your example, makes it do a ton of damage/cause strong conditions/both.