Capture points will be very hard to capture if the enemy has unlimited health. I can see the top sustain solos making a big appearance in Dominion because of their sustain abilities coupled with high burst (Morde, Udyr, Warwick, Lee Sin, etc). Also the healers will make a big difference if they can stay alive and turtle near a point.

Don't you agree?

Maybe Exe Calling will make a come-back.. Or maybe Riot will nerf sustain enough to stop the sustain meta from forming in Dominion.

Nope

Except sustain is getting big nerfs, so not really.

Sustain is actually getting nerfed, and either way sustain is more useful in a laning phase where it completely nullifies harassment, rather than full on fight to the death battles. There is far less defense in Dominion it looks like, and even great sustain characters didn't come off as overly game changing in the stream today.

there is a -20% healing reduction constantly in effect in Dominion. Also, the matches are so fast paced that Soraka (et al) would only be able to get off 1 or 2 heals before a death.
trust me, Riot has thought of this.
Edit: also, turtling is completely impractical. No champion will survive a 3v1 gank, and you can't guard 3 points without leaving only one person at one. That one person would immediately be ganked by the enemy team.