Just some of my thoughts:
As others have said GW is a step in the right direction, sure it could still use a bit of tweaking, but it's a positive step regardless.
I agree with the call that defense teams needing a reason to be creative (whether it's colour bonuses or something else), otherwise we'll just see Devours and Death Marks abound to try and get a lucky troop kill or two.
However, I don't understand the idea of "opting out" of Guild Wars. People seem to be of the opinion that if you do guild wars you MUST use a full colour team. And this isn't the case. Yes, you don't get as many points, but unless you're in the top of the top, this probably won't matter.
This is also what my guild does, we haven't specified people need to use an all colour team, and a number of people haven't, on top of that we have a few people who haven't done their battles at all yet this week (or only the first day or so), and we're still second on our bracket leaderboard by a decent margin. (yes it's early days with seeding and all that, but still, it illustrates the point)
The full colour requirement is only necessary if you assume other guilds are doing the same. What will likely happen in practice is that some people will try for full colour teams for the added challenge, some might throw one or two coloured troops to shake things up a bit or try to help the guild, and others will just play GW as if it was a normal ranked PVP.
And this is where I don't get the "opt out" part... If you decide to not follow the colour team bonus, GW becomes just like normal Ranked PVP. You get trophies, you get PVP rank points, you get increased gold income, you get glory, you can complete PVP related events, and you get the 9 seals. Yes you are in theory "letting down your guild" but only if your guild is trying to maximize their score.
I think what we'll end up seeing is some guilds requiring the colour bonus, and these will bubble up to the top brackets, and other guilds will not, and will do as mine and @Whiskeyjack's guilds do; talk and strategise, but at the end of the day, it's more about the member doing what they find fun.