Frankly, with or without groups of some kind, people can, to put it bluntly, fuck shit up.
I've seen this in action on WoD games as a problem child more than on games that were not, really. As a result, though, I'm speaking in broader terms based on experience with both.
Take a basic XP spend. In WoD terms, this is a spend on a skill or attribute. In a system where all characters function under the same ruleset/powerset, it could arguably be anything. 'Sphere staff' setups in WoD could handle anyone's basic XP spend, as while some spheres have special discounts or rewards for certain skills based on type, it's not hard to write a staff cheat sheet on this, and/or note to players, "Hey, if you have any special conditions related to this spend, put it in your job." (I favor 'and' because even clueful staffers sometimes overlook or forget.) There's no reason any staffer at all can't handle a spend like this. WoD is the only place I've seen people forcibly divide this up and it's an example of where the sphere model breaks down. This is the kind of job I think any staffer should be willing and able to do under the heading of 'basic jobmonkey'.
(I need to stop agreeing with you, @Derp, really this is getting weird!) But like @Derp says, some people are more knowledgeable in certain areas than others. Not everyone is qualified to make any given judgement call on the game, and this becomes more and more the case the more groups there are on the game that require tending. In a game like RfK, with one super sphere and m/+, it's not hard to learn everything. Now try applying that logic to TR and imagine the chaos that would have ensued. You would not have found many qualified candidates for staff at all under those circumstances. Also, I've seen 'the jack of all trades is master of none' proven true more times than I can possibly count, so frankly, in WoD, this becomes an absurd expectation without someone who can handle certain special cases because they're the person that knows them best, and has ideas most in line with headstaff's intended direction for the game.
Again, I have seen the 'too many cooks' problem in action. If I was running a TR-style game, I would stick to the sphere model with a middle-level authority to filter the heavy duty judgement calls for any given group, though 'basic jobs' would be open to any admin to pick up and do.
Personally, I wouldn't allow the 'no one but this sphere is allowed to play with our toys by staff fiat' other games have permitted under the authority of a TL/sphere head/whatever, which is one of the primary problems people have with the sphere system. But again, this is a headstaff call as to whether or not that is allowed as part of that role's authority or not.