Praxic Blade does this right. It seems really silly to me that your only means of defense with a sword is also tied to what is typically your strongest offensive move. Also need to mention that most sword frames and exotic swords have had their heavy attacks nerfed once, or even several times, to the point that using a heavy attack (on most frames) while in a damage cycle is actually a large detriment. So this is to say, I don't think the ability to spam full strength heavy attacks would necessarily be a problem for balance, especially in today's very anti-sword sandbox. Even if it were, just put an equivalent internal cooldown on them, because players already aren't able to spam heavy attacks with any real effectiveness. And on a mostly unrelated note regarding Worldline Zero: after several unnecessary "reworks" it is still very inconsistent / buggy and just doesn't feel fun to use anymore. The "damage buff" it received didn't seem to help. Just very disappointed how one of my favorite niche exotics has been ruined with needless overcomplication.