First, let me get to this:
I am pretty certain that Razorwing works exactly like an Archwing. Last time I've tested Archwing, it counts as being on the ground (Yes, I understand that it sounds ridiculous). I've tested this with Atlas, as his passive requires him to be on the ground. You wouldn't get knocked down during Archwing.
So mods like Aviator, Agility Drift and Aerodynamic do nothing while in Razorwing.
Now onwards to why I think she's fine as is, "even" in comparison.
Not every warframe has to perform equally in every game mode.
Furthermore, I find it a bit sad that you(and others) reduce her to her Razorwing. Here's what my thoughts are on the other abilities:
Her 1 can double as CC or Support ability, not only reducing damage to 0%, but also making you and your allies immune to pesky status effects.
Her 2 gives you and your allies buffs that heighten defense, or reduce enemy speed - both giving you more survivability - as well as buff damage output a little.
Her 3 isn't where it should be. This could use a rework, but only in the quality that you should be able to control where the lantern goes.
She can do a good ammount of things if you are ready to play her outside of her four.
Does Titania need an urgent rework or even an overhaul? - I say no.
Does she need a looking at to get her up to date? - Sure, but there's other warframes that require more attention.