I am not expecting the Titans to use many 3 WR sets.
I expect the Titans to run the ball a lot and most common personnel grouping to be 2TE or 1TE 1FB.
The starting 2 WR will likely be a rotation of these WR and being able to block will be important for getting a lot of offensive snaps.
DGB and perhaps Hunter might be the best blocking WR on the team.
I still have not seen DGB track the ball over his shoulder. Every route he was targeted on last season had him coming back towards the ball. His ADP has been consistently higher than I think he is worth.
I agree with the Fresh Prince that whoever does well early and becomes the hot waiver wire pick up may not end up being the best WR for the season. I could see the hot hand changing week to week.
I do really like Mariota, (although the offense does not help him in fantasy right now) so if one of these guys becomes his favorite, that WR could be valuable.
For dynasty I am not sure who the Titans head coach will be in 2017. If its Mularkey then situation continues to be less than ideal. Maybe you could count on Mariota's favorite carrying over into next season. If the coach is someone other than Mularkey, I would see most of those scenarios as being a positive, just because of addition by subtraction. Mularkey may be worse than Wiz was.