In a nutshell:

On the way to the Theramore Summit, Katrana/Onyxia captures Wrynn and performs a ritual that splits him in two. Lo'gosh is the "warrior" half, and Wrynn becomes the more jovial half. Wrynn is captured by naga and ransomed back to Stormwind.
Lo'gosh escapes and ends up washed up on a beach in Durotar with no memories. He then becomes the best gladiator ever (apparently), does lots of stuff and finally remembers "Oh, I have a kid to save and a nation to rule" and heads back to Stormwind.

Cue events above.

In Onyxia's Lair, Lo'gosh and Wrynn fight her, crazy stuff happens and somehow the two join back into one person, and kill Onyxia (supposedly with the support of a large group of NPCs in the backing - apparently these represent the players).

That's about it really.


In regards to the details about the comics, I do agree there's a lot of lore here, it'd be nice to have it in comic format AND available in-game (just a couple of NPCs discussing "recent events" would do). The artwork of the first series (The gladiator part) and the Ashbringer comic, is done by Ludo Lullabi, and personally I'm a fan of his artwork.
The artist of the second series is described as bringing a "refreshing kinetic artstyle" to the scene... frankly, the last time someone used the term "kinetic", it was an orb that hit the floor and wiped the raid. The art style is little different.