SS isn't getting a buff. It simply won't be useless.

Previously, roughly 50% of a summoner's dps was from dots, so SS was 50% efficiency.

Now it'll be 100% efficiency. We'll see if it is actually worthwhile, and if mana will be an issue.

For example, lets assume 100SS increases dps by 1%, well if 100 crit still increases dps by 1%, then we'll still go crit, because it doesn't have any mana inefficiency issues.

You see the point here, unless SS is overbalanced in that it provides more dps/point than other stuff, it won't be used, it is still the least useful of the stats, if we assume similar damage contribution.