If we're talking strictly from a point of view that Viable = Consistently Powerful, then absolutely no, Talon's kit is heavily reliant on gold and items to function due to his assassin nature and he has no utility outside of damage. Hes got low range, sustain tied to creep killing (which hurts your ADC), roaming capabilities far below that of other supports despite that being what most of his power is put into and an extreme weakness to poke and harrass from ranged champions.
For fun, its absolutely a blast. Otherwise, steer well clear. It's basically like a Pyke without any of the cc or poke protection.
Basically. It won't work unless your opponents are incredibly stupid and your team is very aware of what youre doing, which requires incredible coordination, and you'll probably leave your ADC out in the cold, and in the hyper carry meta we're in, ADCs are incredibly valuable.
Viable? No. Enoyable? Yes.
Thats the most serious answer you'll get.