I mean, when you boil down to it, it's about parasitic/linear mechanics, right?
For (maybe interesting?) context, Scars has an as-fan of poison of 1.2. To get that in cube, 8.5% of your cards need to have poison, which is what, 30 cards (in a 360 cube), which is maybe two drafters. That's not counting proliferate, which would contribute another 6 cards if taken directly from scars numbers.
Uh, I don't know if linear really applies, but, parasitic, yes. Mechanically isolated. Proliferate was an attempt to tie the Poison and Metalcraft themes together, but I don't think it was particularly effective.