You sure? That's not the result I was getting from my tests, everything worked out exactly as expected re : my post on Liandry's.
Unsurprising, as it's intended to be a proc from spell damage, not item damage.
That's not the issue, really. The issue is that Swain needs defences, and Liandry's simply doesn't give enough of them. Realistically, it's not a bad item in terms of damage since you're spreading it over the entire team in teamfights; it's simply the fact that Swain attains his power by being unkillable, not by being bursty. The only pure damage item Swain should ever consider is deathcap, and even that is your 4th or 5th item.
I made sure to test it like this:
Tides of Blood, wait 2 seconds, transfusion. However, the icon symbolizing the DoT disappeared within less than a second after transfusion. I didn't pay attention to the floating combat text, however, so either it does not get reapplied or it's merely a visual bug.
Also, on #2 I just wanted to restate that what OP wrote was incorrect.