Water's boomerang ability is hardly a consolation for needing range when you're stuck with daggers. It's an option, but a poor one.
And if you got stuck with hammer/greatsword on your Guardian, that's a failure on your part. Here's where you're starting to pick up on the differences. I can choose to equip hammer/greatsword on a Guardian and it's a personally limiting decision. The option exists, and I could probably come up with some compelling reasons to do it that way. I can also choose to run around everywhere with daggers on my Elementalist (as I often do), but I don't get the same option the Guardian does. If I needed the flexibility of range and melee in a given scenario I'm screwed. It's one or the other.
Yes there are 4 attunements, but they are all very focused to a combat role based on the weapon(s). Daggers are clearly "close range". Scepter is more "medium range". Staff obviously covers "long range". Off-hands compliment. There is a small amount of variability within those roles, but not enough that an Elementalist will ever have all the bases covered in a given fight to the degree that some classes can (keyword). The option does not exist. And that's where the weakness comes from.
Having said all that, I'm going to go back and try more PvE stuff with scepter+focus and see how it fairs. It may be a viable compromise.