Brave Ike IV question

I believe that there is a wide range of opinions on what best B.Ike IV means.

I have a +spd -res Ike currently and earlier I had +atk -spd. Speed is a superbane I believe, so you'd be staying at Dorcas levels of speed.
My -spd Ike would sometimes get killed during melee encounters by getting doubled, which is something that doesn't happen now because he evades so many follow-ups and I believe that the neutral speed version would also benefit from it, although I'd advice you to check how those IVs do on a mass combat simulator.

Also, Ike doesn't need to get doubled by the enemy in order to trigger Aether in the same round of combat, because Urvan already lowers your cd by 1, which means that (when enemy attacks and using steady breath) you will get 2 charges from the first enemy attack, then you will get 2 from your own attack and then you will blast them with Aether on your second attack (with QR). This makes Ike extremely tough to deal with on close range, because not getting doubled too often and then healing back up is just so valuable, because you lost way less hp by not getting doubled and you are also evading the risk of getting blasted in your face with enemy's special.

+def -res would be my advice here so that you can make him focus on a matchup where he truly shines, but as I stated above, it might be worth checking the mass combat simulator to decide for yourself, because the +atk -hp version could also be worth a shot.