Personally I think it'd add a needed escape to her kit without being too OP.
To be able to jump in then jump out she'd have to mark the target with Q to get the double ultimate.
She'd be ultimately sacrificing damage by putting her ultimate on full cool down (because you can't mark friendly characters / wards with Q), so there'd be a nice trade off and decision making element to it as well.
Thoughts?
Photos of Ghosts4 votesShe'd need nerfs elsewhere cuz she stronk atm, but it's true that if you go assassin on her you'd need an escape.
iainB851 votes[{quoted}](name=Photos of Ghosts,realm=EUW,application-id=3ErqAdtq,discussion-id=VAwbNURr,comment-id=0000,timestamp=2015-05-13T18:06:44.167+0000)
She'd need nerfs elsewhere cuz she stronk atm
Maybe... I just think it'd make her kit a lot more fun. Currently she hits Q, and if she commits to the R she's pretty much all in. No room for outplays or any decision making past that.
King Odin1 votes
all have no escapes if they all in which is supposed to be the way an Assassin is played. High risk for high reward not like 
cough
iainB851 votes[{quoted}](name=King Odarth,realm=NA,application-id=3ErqAdtq,discussion-id=VAwbNURr,comment-id=000000000000,timestamp=2015-05-13T18:14:25.790+0000)
All those champions CAN use their ultimate (or in Shaco's case Q) as an escape though if they are in a bad spot. Diana can only do this on the off chance an enemy character is near by that she can jump to that won't also kill her.
King Odin1 votesNocturne can not and let me add 
to the list
iainB851 votes[{quoted}](name=King Odarth,realm=NA,application-id=3ErqAdtq,discussion-id=VAwbNURr,comment-id=00000000000000000000,timestamp=2015-05-13T18:17:34.168+0000)
Nocturne can not and let me add
Nocturne can if they aren't all grouped. Probably the most limited with Diana.
Yasuo can jump to ANY target, making his escape still far better than Diana's.
Akali has shroud that stealths AND gives movement speed.
Just saying, these champions (with the exception of Nocturne) all have more reliable disengages than Diana does.
King Odin1 votesDiana can jump to any target and further too. Yasuo has to be a lot closer.
King Odin1 votesHer being able to Q over and ult to a minion or monster allows her to escape well enough atm. Not every assassin necessarily needs a guaranteed escape especially since she can ult twice if she hits her first target with her Q. She'd be broken if this were to happen and would just be an AP version of Lee sin with more damage imo
iainB851 votes[{quoted}](name=King Odarth,realm=NA,application-id=3ErqAdtq,discussion-id=VAwbNURr,comment-id=0001,timestamp=2015-05-13T18:11:08.947+0000)
Her being able to Q over and ult to a minion or monster allows her to escape well enough atm. Not every assassin necessarily needs a guaranteed escape especially since she can ult twice if she hits her first target with her Q. She'd be broken if this were to happen and would just be an AP version of Lee sin with more damage imo
More damage but far less utility.
Tmoose1 votesI think she is strong enough already
Wînter Fox1 votesThat defeats the whole point of the champ. She's supposed to be an all-in burst aoe fighter. That's what makes 
so core on her.