This is something that affects 3 hit and 2 hit swords like Calibur and Avenger respectively. Slightly noticeable on 3 hit swords, very noticeable on 2 hit swords.
With 3 hit swords, sometimes my last hit won't connect. With 2 hit swords I can actually see the mob being pushed back further than my follow-up lunge travels (even taking into account that the follow-up lunge has a longer range), this will almost always cause the last hit to miss (unless I'm face-hugging the mob, but even then, sometimes it misses) and because the first hit doesn't actually stun or make the mob flinch, it is free to just walk up and hit me because I'm now stuck in my finishing animation that I can't shield cancel out of. (The finishing animation for 2 hit swords is also much too long but let's work on one thing at a time shall we?)
I suggest you reduce the knockback distance on attacks which come before the final hit or just revisit the way sword combo's chain entirely.
Part of the reason to take these swords is BECAUSE they knock back on the third hit. If you need the knockback, you go for the 3-hit combo, and if you don't you just do two hits and block, then repeat the two-hit loop. Getting swarmed and not having that knockback... I can't support it.
I am strongly against changing current weapons. However, I would not be against adding a new sword line that has no knockback.