Mr.E
unban me from Discord
It's not remotely the same thing, since Swain can easily chew through infinite mana for having his ult active a long time. Of course, ideally you should turn it off before it gets too costly but it's not a insignificant amount of time you have to sit out of the fight waiting for the cooldown to come back up to get back in. Swain can't exactly do much once you turn off his ult and you can't always afford to just shut off mid-fight and sit out for the next ten seconds.I'm quite sure he isn't. It's just you don't need it on Swain.
If you plan on justifying it on Swain, I'm sure we can all remind you of why people buy LW on Vayne.
Although the obvious thing I missed was the suggestion to rush RoA, so *shrug*. But Grail and Morellonomicon both have mana regen anyway if you're gonna itemize CDR (are you really going to buy DFG on Swain? ...maybe), so you're probably gonna get mana regen whether you like it or not.