So rogues and paladins don't get spam, eh? *makes note*
But seriously, could level affect it? Do you have a wide range of levels, and do high level characters get it as frequently as low levels?
I haven't noticed a difference in the amount of spam I get and the amount of spam my friends get. I have a very wide range of levels to myself, because I enjoy making more characters, however, my highest level char is only a 44 shaman. My friends are 50, 54, 58, and 58.
58 Night Elf Druid
58 Night Elf Hunter
54 Night Elf Priest
50 Human Warrior
44 Draenei Shaman
and then aside from the shaman I play my 34 Gnome Mage alot too.
My friend that is the priest used to play his 42 Human Warlock a lot, but he hasn't been on it for awhile. I also have a 18 Undead Warlock that I play PvP with a lot and it gets spam too. When I am able to get on again I will ask some of my 70 friends if they get a lot of spam.
My list of chars:
44 Draenei Shaman
34 Gnome Mage
18 Dwarf Paladin
16 Night Elf Hunter
11 Gnome Warlock
7 Night Elf Rogue
7 Night Elf Druid
All of those are on the Frostmane Server
On Aegwynne I have:
18 Undead Warlock
10 Tauren Hunter
2 Blood Elf Priest
And on one of the other random servers that I don't frequent anymore I have a 8 Troll Shaman. I haven't been on there for over a month though.