Wow I have never ever had this happen to me. I get pretty much nothing but praise in groups. Having been a long time Raid Tank (guardian) but having burned the heck out after tier 6. I swapped to playing my mystic and my ranger. My tank is now my tradeskill main and only goes out to adventure when friends need help.
As to us being melee specced, aren't most of us spec'd for melee. Not like we have alot of choices. Being the only mystic in our raid force, and being specced to be a healer first and melee second. I get more ribbing from my raid for not putting up a parse then doing it.
My raid leader defines my role as debuffer> cures> warder/healer> melee in exactly that order. I am always in the off tank group because our best ability can be cast cross raid, and I use my single target ward while the main tank defiler uses his group versions. This way we stack no overwriting. Now granted I have been raiding for a long time and know for the most part when I can get in there and add my dps to the raid without causing any problems for my group or the tanks.
As to grouping hell even in pickup groups no one gives me a second thought when they see me standing behind the mob shoving my various weapons up his [Removed for Content].. lol ...
I will tell you a trick for getting peeps to love you ... make your macro's with tells to the group (use your imagination just don't over do it) about what you are casting. Such and such spell being cast now on X. Ect ... group heal inc, group cure inc in 2 seconds ect ect. I get more tells from peeps that haven't grouped with me before for being the most on top of it healer they have ever played with. What they don't know is that I simply am to lazy to setup non raid centric hot bars. In my guild we have language issues so we don't use Vent we use raid chat ect. So every single major cast is announced to my group, some of them to the raid to let our healing corp's know what I am doing ect. Same thing from them. It works [Removed for Content] near flawless once you get used to reading the scrolling window while your fingers automatically do their jobs hitting your spells in the casting order needed for the mobs you are fighting.
Anyone these days that slams you for being melee specced probably is in a sucky guild that doesn't utilize all the tools available to them, and most likely isn't clearing all EOF content.