Yeah something really didn't sit right with me after I verbalized everything and when I went back to check, I saw that I'd made an error. Rather than redo the video (or even worse, ignore the mistake) I thought that tacking on a small video discussing the mistake (and fixing it, of course) would be the best course of action. 
There are definitely a lot of TAGs that will raise their flush draws, and there are DEFINITELY benefits to doing so. These include
- FOLD EQUITY: Obviously, raising gives us the chance to make our opponent fold (either because we are repping a strong hand or because he has squat and doesn't want to risk a huge portion of his stack to rebluff us). Keep in mind that this benefit works best when either our opponent's range for opening/cbetting is fairly wide/weak, or our opponent will fold with decent frequency. (next episode, I plan on talking about how fold equity and pot equity combined will determine whether or not a play will be profitable). Remember that even if raising is profitable, it has to be weighed against our other options (which involve calling, either with the intent to float or the intent to bust a big (but worse) hand that won't fold.
- BALANCE: If we're going to be playing against observant regulars, we really can't afford to have transparent ranges (meaning that we always do one specific thing with one specific type of hand). If we're going to be fast-playing our very strong hands on the flop, to balance, we should be raising other types of hands as well, and draws are a very good hand to do this with. If our opponent has to guess as to what type of holding we have, it's less likely that he can play perfectly against us in this spot (again, by perfectly, I mean playing the same way he would if he could see our cards). Of course, we only gain this benefit if we're playing against an observant reg, and to boot, we do lose some opportunities to balance our floating range.
Much of the information in your post answers the questions in your second to last paragraph.
Raising a FD will be better than calling when either you think your implied odds are bad (and thus, your fold equity is good). Lots of things can make this happen. I like to look for people who cbet a ton and don't play the turn really straight-forward, or people with a high "fold to flop raise"% (which you can put in a HUD popup...I have mine in the "cbet" popup). Wettish boards are also good, but severely wet boards may be better for calling. The reasoning there is that on a severely wet board, there are a ton of cards that your opponent will hate that you can rep quite easily and if he checks to you, you can bet and take it down. As always, knowing your villain (and your history with the villain) will be a great guide.
If we have the odds to call, then I feel that raising would solely be a balancing play and it'd really be up to you and your style. The implied odds/fold equity balance would also play in, but if your direct odds are good, calling will be a mistake FAR less often than raising will be. 
Direct odds, regular odds, immediate odds, and express(ed) odds all refer to your call vs the pot size. I'm pretty sure I've seen it written as both "expressed" and "express" but not sure enough to put money on it. lol "Expressed" does sound better as well, now that you mention it. Thanks again for posting questions!