Just wondering which to keep, since my Phasegrasp/Ties That Bind does no normal damage.
I would check out a YouTuber named moxsy. He just put out some videos regarding this subject.
Doesn’t his video just cover everything we’ve talked about on the forum?
Can’t wait until a video I made to break down Vampyr. 
Not sure. I haven’t see everything that was covered in the forum about infusion. Just figure it’s a good reference and can save some time.
I saw his video. His testing shows that infusion on a non-elemental weapon will not proc sustainment. Ties that bind procs sustainment no matter what gun you are using.
Also he figured out that infusion DoT damage when using the same element no longer overwrites the bigger DoT from the gun, but that infusion instead now drops the main DoT by whatever percentage of infusion. This must have been stealth fixed since infusion DoT used to overwrite. He was even shocked when he did his testing because he assumed for his video that the lower DoT would overwrite. It seems like they fixed it by disallowing infusion from producing a DoT if the elements match.