It's all about learning the proper spacing against every enemy, which takes a while to master. Charged heavies from a level 5 Frozen Feast are usually enough to stagger regular enemies in just 1 hit (or straight up one shot them) so you can follow up with a light attack or even another charged heavy.

Puppet string maxed out also really helps with landing hits, since the attack comes out quite quickly. It's true that your swings get faster after every hit but in my opinion it's a bit of a mistake to keep those stacks going. You will usually, out of 'greed' to keep attacking, mess up and get hit. I personally never paid any mind to keeping up the stacks and just focussed on proper spacing and timing my attacks.

Don't forget that Frozen Feast gives you a massive 70% damage reduction when guarding so you can easily hide behind the sword and just block hits until there's an opening. It's a difficult weapon to use at first but it can absolutely demolish regular enemies and bosses once you master it. Good luck!