In my opinion when you have five damage items with the hydra active that's more than enough damage to blow up a carry which is why I tend to get a defensive item
Here's why I think boots of mobility are better than lucidity and merc (in most situations)
Talon is a roamer..there's absolutely no denying that. Ever since he lost his silence his ability to solo kill in a lane got more difficult (not impossible but it isnt easy either). The ability to move up and down jungles really helps Talon quickly get to a side lane to gank or get back to his lane without losing too much cs/experience
Lucidity sounds nice on paper but tbh Talon's ult is already on an extremely low cd anyways soo I don't think you really need it
Merc is good if the team has super heavy cc
But I prefer roaming with Talon over everything else
I also don't really like the bloodthirster pick up simply because Talon isn't an AA reliant champ...So the life steal he receives is extremely minimal...Black cleaver like I said is a good item but I think there are other items you can take.
Remember even though Talon is known to be a suicide bomber doesn't mean you act like one. Talon if he's able to survive and wait for cds can do a lot of damage with just an e-w-q combo.