In Game Threat Meter

Q u o t e:
Call me asleep at the wheel; however; I have been seeing something about this subject, but then again not much information. Is there one and how does it work? Is it something a solo kind of player really would not see in the first place, seeing as how outside a pet, the only threat is with the player.
Silly me,
A~

It's in there =).

If you open your options menu, then select display from the sub-menu, there will be a pane with several options on it. One of these is entitled 'Display Aggro Warning', and it has a drop down beneath it which allows you to set when the threat meter will display. Just below that, you can choose to display aggro as a percentage by checking off that option.

It's a good idea to make sure that 'preview talent changes' is checked while you're there. That way, when you respec, you can choose talents just as you would when using a talent calculator (left click to add, right click to remove), and then finalize your choices after you're satisfied with your spec.

I hope that helps!