What Irelia really needs is a shift of power.

And this is not likely going to be just one large change but a bunch of small and medium size ones.

A shift away from team fighting to a degree and a bit more power as a duelist.

Examples of what could be done? Just the direction I would try to take her.

If using bladesurge to a marked enemy the cooldown is reduced by 70% instead of refreshed. Making it so that her burst is slowed down. This would mean that a 12 second cooldown at rank 1 of the ability will be reduced to 3.6 and at max rank with 40% CDR it will be 1.44 seconds before Bladesurge can be used a second time. This will also push for the old leapfrog on a minion being more relevant to get close to an enemy. Bladesurge will still get a refresh if used to kill the target.

With a reduced amount of burst Bladesurge can now actually do more damage than an auto at low levels 20/35/50/65/80 + .8 AD.

Ult no longer disarms. Her team fight power is proving to make her dangerous even if behind. Damage can also be reduced if that is a big issue with her burst.

Base AD increased to be closer to most fighters 64 to 130 up from 60 to 128.

Passive nerfs at least partly reverted. It went from having decent base + total AD to less base + bonus AD. Usually abilities have one or the other but in this game a bit of both. Passive now does 2 to 14 + 1.5% to 3% Total AD per stack.

With her burst reduced it is not out of the question to make her stun duration a bit higher or at least scaling with rank. .8/.9/1.0/1.1/1.2 stun duration.

Target of these changes are to make Irelia better at sustained damage and better able to contend with rough match ups while tuning down her burst.

Note that I am not trying to give her more power than she already has just shifting her away from burst and team fighting to some degree while improving her laning phase and sustained damage.