No, I think it's fine to use the 2-minute rule!
You either spend the 2 minutes and actually get the thing done; or you spend time
now deciding where it goes in your system and putting it there, and you spend time each time you review your someday/maybe's reconsidering whether to do that thing or not. I think David Allen has figured that about 2 minutes is the cutoff where it won't be worthwhile to put it into your system rather than do it now.
You could have two different types of 2-minute someday/maybes: one is the type
where the whole project will take 2 minutes; i.e. there's only one action in the
project. It's probably worthwhile to do those when you run across them. The other
type is where you can do a 2-minute action, but it won't actually do you any good
unless you eventually do a bunch more actions on that project. Maybe it's still
good to do those; or maybe you could set a 1-minute or 30-second rule for those
instead; or maybe it depends on whether that 2 minutes of work will still do some
good if you eventually do the rest of the project 3 years from now.
It can also depend on how busy you are. You could make it a 30-second rule or
a 5-minute rule depending on how much you're in a hurry to get through your
inbox right now.
Or, just keep it simple as always a 2-minute rule so you don't spend a lot of
time standing there thinking "Let's see: shall I apply a 2-minute rule or a 1-minute
rule to this one?" Actually, I find I can make those decisions quite quickly, usually.
I figure if it's close to the borderline, then it doesn't matter that much which
way I go. (The derivative is near-zero near the maximum, as my father pointed out.)