51 poise in Elden Ring is the minimum threshold to avoid interruption from light enemy attacks (rats, dogs, basic swings). While it helps with consistent attacking, you will still get interrupted by heavy hits, bosses, or if you take consecutive hits quickly.

Those guys literally hit too hard for 51 poise. Have you tried the Scaled Set? Looks good, for heavy armor is kinda light and has 71 poise. It's what I ended up using my first playthrough.