I didn't know people would dislike the new voice act for the Outsider. I didn't even know it was a different voice actor into I saw this Polygon article. Personally, I thought the Outsider in the trailer sounded the way he did because of possible anger towards the main villain of Dishonored 2 and the Brigmore Witches DLC. Also, he sounds a bit more alive, whereas the original outsider sounded like he was whispering in my ear (which was a strain at times when trying to listen to him).
My opinions on the new Outsider voice (Robin Lord Taylor - Penguin from Gotham) are as follows:
1) Canonically it was confirmed that the Outsider was merged with the void when he was a teenager.
I believe it was confirmed in the Dunwall City Archives (a physical book that came out), as well as Harvey Smith confirming it.
Therefore, I'm perfectly fine with him sounding "younger," or even having that teenage angst toward Delilah and the Duke (as you pointed out).
I also agree with you on him also sounding more alive in this one.
2) I would have LOVED for it to have been Billy Lush for the sequel again, for whatever reason Arkane chose to go with Robin Lord Taylor instead.
That said, much like with how it took me a little bit to get used to the Outsider's voice in the first Dishonored with Billy Lush, I'm pretty sure that by the 2nd or 3rd playthrough of Dishonored 2 I'll be used to the new Outsider voice.
It's just the same way that I got used to the voice announcer in the newer MK9 and MKX games (Jamieson Price), instead of having Steve Ritchie.
It's not that big of a deal for me, regarding Dishonored 2.