@Ardena
I've never used SLDataTexts, so I don't know. I use Fortress and a collection of LDB addons instead.
TipTac has a lovely default tooltip, and I've had no need or desire to change it's default display, except for customizing it's display of HP and Mana bars. It's written by Aezay, and he's very good about keeping things very configurable.
I believe the guildrank line can be changed like so:
Code:
[classcolor][if isinguild then guildrank " of " guild]
I'm not CERTAIN of that "isinguild" bit, but you may be able to check the DogTag Help that's in-game in CowTip. It SHOULD have something similar to that.
The unitframes I use (StUF) also don't use dogtags - they have a simple, small built in tag section, and can also be set up to use lua.