Recently I have been kicked out from the party (actually i left by me own choice , but leader recommended to me to do it), because I confessed that my toon Azaxe as Sorc don't have the Quicken feat. Citation: "You are playing Sorc without Quicken, Really, really?..."
My first toon was the Sorc until level 17. My second toon was the Sorc too until level 25 then she TRed. My third toon is also the Sorc and she is currently on third epic life (2x ER).
None of these Sorcerers had Quicken feat. I remember times, when Toughness was must have feat. I appreciate that this game has many alternatives how to play it. So why "must feats" requirements? Why quicken? Sorcerer is the fastest caster in the game. Only benefit from the Quicken is to remove possibility of an interruption. The chance of the interruption is still very low, because casting really fast. High concentration also helps. So for me, Quicken is waste of the feat slot.
My favorite feats on the Sorcerer are: Dragonmarks (because I am playing with Halflings - for healing), Maximize, Enlarge (Shocking Grasps, Electric Loop, Irresistible Otto), Heighten, Evoc Focus, Greater Evoc Focus, Force of Personality for saves. At the epic level with the Cocoon from the EDs, I can swap Dragonmarks for Empower.
I have Concentration 54+. It does mean, that occasionally my caster is interrupted due an incoming damage, but this isn't big issue, I can live with it. To avoid the damage complete is the goal.
Anyone has also experience with requirements to "must have" feats?