Is Vel'Koz support viable in Gold elo?

If you play him well I don't see why not. I've seen a few around high plat/low diamond and they are super annoying.

Absolutely

First off, don't use the word Viable.

it's a term used by the lesser of your piers and generally what they really mean by using it is to admit that they don't know what they are talking about and don't have enough knowledge of something to make a determination about it. No one has to ask if Ezreal Jungle is viable if they know that Ezreal Jungle is fine.

You don't need anyone elses opinion on whether something is good or not. Either you can make it work or you cant, simple.