I think 60% unique is excellent for game flavor.
I'm having a hard time siding with you Stags. I think maintaining a strict gold curve which guarantees a high-card flop is an obvious part of the game. If the decks have a high number of low cost cards, few with the limited keyword, then you should be able to reliably flop 5 cards unless your deck is an army deck or some other theme that really depends on high cost cards.
If the real complaint is that people are building decks that get higher flops than yours I'd say that you should be looking to your gold curve for characters and locations. Please understand I'm not trying to tell you how to play or build, just pointing out that deck that is composed of 60% unique characters and still getting out 5 card flops contradicts (at least to me) the idea that the deck is full of generic no names. If a swarm or weenie deck is any deck which effectively uses weenies as cannon fodder and foot soldiers to supplement the cavalry and officers, then we are just going to have to agree to disagree. That is how armies are fielded for a reason. It wins military battles. It is efficient, gets the job done, and lets the specialized units do what they need to do while the grunts keep everyone else busy, and yes, pay the cost when necessary.
It is no different in power struggles or intrigue gambits. The major conspirators define the strategy, and direct their subordinates, minions, and unwilling or unknowing accomplices do all the grunt work and get the axe when caught.
I don't think a weenie reset plot will have the effect you think it will if these are the types of decks you are facing.
A swarm/weenie deck to me pretty much always relies on the lowest cost characters possible, especially the ones with stealth or deadly, and flooding the board. Forcing the reset as early as possible and re-flooding the board and just opposing every challenge when possible and sending more characters at them than they can manage. You may have 4 or 5 characters in a 35-40 character with a cost of 3-5 depending on their abilities and whether they can act like a hammer when the little guys can't get the job done. About the only thing that really stops this kind of deck from a plot perspective is multiple resets. What they are is of little importance, it is just keeping the numbers down to manageable levels as often as possible. Multi-claim plots, strong ability to defend, ways of grabbing and protecting your power, are the best ways of getting through a swarm deck when backed up by multiple resets... though I suspect you know all of that.
The problem is First Snow never hurt my weenie decks. No single reset ever does. What it did was destroy my decks that depended on utilitarian low strength characters to fill a hole in my regular decks. My various maesters in Martell, my holy crested characters in Greyjoy, etc. where the ones getting wiped out, meaning my draw was crippled, or a sudden loss of my intrigue icons.