Skyrim needs more factions, yes, but first I'd like to see the existing ones made better. They all kind of suck. The Thieves Guild questline was the best, but it wasn't based mostly on the guild, rather, the Nightingales.
The the DBH was just mainly the same thing: Get contract(s), kill them, go back, get contracts, etc. Boring and repetitive as hell. Not to mention it felt extremely shallow, predictable, extremely WTF worthy, and the characters for the guild felt the same.
The Companions questline was short and shallow, and the quests you get after it are, for the most part, suffering from the same issue as the DBH did for its entirety and what the Thieves Guild suffered from after completing the main thing: easy and unoriginal quests that drag you all over Skyrim for one little thing, then all the way back to headquarters.
The Blades suffers from a lack of choices right off the bat. Kill Paarthurnax. That's it. You can't even say "no, F you."
Oh, and the Civil War questline (Imperial/Stormcloak faction) had the same issues: short, repetitive, unoriginal, boring, and, unlike most of the others, horribly easy.
PS, what is with all the purple names now? I have not been on lately. Did I miss something?
The purple powers are article writers. Check the front page.