That's probably up for debate. In the example above, I said they might be "solvers," that is, characters who remove barriers to progress. They'd probably do it in a few different ways, with a few different Magic-related skills. A skill like Teleportation, or Disintegration, or Riddles, or something. Details sketchy, but whatever helps the party move past an otherwise obstacle is what they might be good at.
"Solvers" is just a catch phrase for everything else. Magic yet again, enfolds everyone else's domain, as well as supernatural stuff that's off limits to the normal guys. So no deal.
Whatever the other characters do get to do. If the rogue is a "scout," then the divination abilities of Wizards and Clerics are crappy and inaccurate at best. If the fighter is the "sentinel," then spells like Charm Person and illusion rituals are error-prone and unreliable. They might still figure in a pinch (like the rogue picking a lot), but they are clearly not what the character is meant to do.
So we're back to the current state of rituals. You get to be a jack of all trades, master of none. You trade speed and free for versatility.
Speak with Dead and Fly might be good "solver" territory, though. They open up new avenues of exploration, which is what a Wizard is probably there to do.
Fly replaces athletics. No dice... you're taking away from mover territory. Speak with dead replaces information gathering. Again, sorry wizards.
This is the problem with your system... "solver" is just the guy who beats the adventure. What the casters were in earlier editions, where they were simply better than everyone else.
A class ability that doesn't get used might as well not exist.
They do in other people's game. You just want the gravy casters get for free to be as good as everyone else skills and powers. If the ritual caster ONLY got rituals, I might agree. Right now, its a third tier of options, and should be treated as such.
I do have a feat suggestion for those wanting to use rituals in combat...
Hasten Ritual
Tier: Heroic
Pre-requisites: Ritual Caster, Skill Focus
While casting a ritual with a casting time of 10 minutes or less, expend an action point and an encounter power of the ritual's level or less. The ritual's effect occurs at the end of your next turn. Until this time, you may only take a move or minor action. If you are damaged during this time, you must make a saving throw or the ritual fails.
Special: You must have skill focus of the ritual's key skill
Something like this might work... it means others have to protect the caster and they have to pay resources with a premium to use what is essentially another power option.