Yep, Guild progression system is one of the easiest thing to come up by for any game, all we have is The Broken Crypt of the Great Lag.
Something you put work into by whole guild would provide advantage compared to someone who doesn't?
Better guilds get better GW rewards, why don't have better perks too if they earned it?
I guess at the end everyone will have them maxed anyway.
I like your perks examples, they are guild related. Really good stuff except faster stamina regen, which is no-no.
Allowing to use hero +5 level is just so hot for me personally, every update I'm cut out of half of the hire because I don't rush levels but because we are in top5, many people get level cap on the first day/contest.