According to Wikipedia "Vertcoin has already forked two times to a new PoW function because of a veritable threat of centralized mining." so it kind of proves my point. They are a great example of my final suggestion of regularly changing algorithms to throw off the ASICs.
https://en.wikipedia.org/wiki/Vertcoin
But as for the bit about "... a memory intensive and growing memory algo which makes asics difficult to optimize for but ideal for GPUs" I think you might have drunk too much of the kool-aid there ;)
Haha yeah im wrong on the memory part but the devs have proven to adapt to asics being developed which is as resistant as it gets imo. You're right that an algo in itself isn't very resistant but what incentive is there to make an fpga asic for vertcoin when the asics made require firmware upgrades and the devs have proven to respond to asics developed relatively quick?
source
Yes, I agree with you. I wasn't really aware of Vertcoin before and the success they have had staying ahead of things. By the sounds of it they've got a good approach to ward off the ASIC developers and are agile enough to go through with it.