I'd argue they still have their merit. Guilds provide a tighter knit sense of community. While you may be benevolent and help out our community as a whole, you still have more familiar players that you can queue with or engage with in chat.
This is amplified even more in my opinion when it comes to scaled epic farms, or any sort of wargame play. Groups for farming will always be inclusive for everyone, but you'll have greater luck getting to know the regulars and people willing to put out large 2x4 sessions.
BG and Arena wargames mean a lot more under that <guild> tag and you'll have routine players to build synergy with. Yes, /4 community will always have you in the know for events, but having a foundation of players to get to know and duel/play with is a huge plus.
While I respect, admire, and compete against the lone wolves of this bracket, I encourage others to seek out their own havens and develop &/or grow with their own nests of players.