As far as exp with light blue mobs goes, I don't know exactly how good it was before, because I wasn't here. But I can tell you that it's really frustrating right now just how little exp light blue mobs give vs dark blue and above. I know they're easier, but they're not *that* much easier.
An example was when we had a group of 4 in Yaralith, around level 20. We were killing mobs that were DB, and getting roughly 1200 or so exp with our current bonuses (1400s and 1700ish on white/yellow). One person in our group of four dinged (just ONE), and some of the mobs turned light blue....and EVERYONE in the group started getting 200 exp on those mobs.
Now, those mobs were just as difficult as they were 5 minutes earlier. There has to be a cutoff somewhere, but should an entire group suffer because a mob is LB to one player? I was surprised that the experience the group earned was based off the highest person's level, rather than a group average, which is kinda common sense, and I believe exists in most MMOs.
Right now we play a group of 4 who are all the same level, and we are working hard to keep it that way just so we get decent exp. At level 26, I have no real desire to invite someone to our group who is even 28, let alone 30, because the exp would be almost worthless, unless we find a spot with plenty of mobs and a moderate amount above LB to the high member. Grouping is the point of MMOs (soloing is fun, but the focus is always grouping), and I feel ashamed to not want to invite someone to a group. It'll get easier I know as the DB range gets bigger (if it does like it did in Live, which I hope), but it'll always exist.
What was the status of LB exp before that it was so abused it had to be nerfed, if I may ask? Kinda curious.
I dunno, it seems like a mob should be based on the level average, rounded up or down at a group's half level point. At least then mobs turning light blue would be more worth the effort to kill, whereas now they're almost as difficult as a DB for us and give a fraction the exp. Mobs could still give no exp if they were green to one person in the group, to prevent abuse.
Not game breaking at all, just frustrating and makes me want to be too selective in group invites, which shouldn't be the case on a small population server. And I could be wrong since I'm still learning, but everything I put in here is gleaned from experiences in SoD so far, which is easily the funnest game I've played in years, btw
* Edited to add that it's not just light blues - if mobs white/yellow to everyone in the group are DB to someone who you potentially would like to invite, you'd lose all that extra exp just to kill slightly faster, too, so it makes you disinclined to invite people all the more unless they are below you in level.