I think I'll still play him. Sure, my chance of sniping enemies to death goes down, but my dueling doesn't really change much. Sure, I lost some power in Precision in my mastery page...but so did everyone else...that enemy Lux will now hurt me less with her Thunderlord's Decree. Got to learn to look on the bright side of things.
I think him losing damage is more important than losing some Q frequency. Even if he isn't great still as a bottom lane carry, you can still support with him playing AP with these changes. It's not like they cut his Q range or something like that. He still gets picked by me for having good poke range I would think.
These changes may be a bit of a bait and switch...intending for players that liked poking with Varus and in general being shitty ADCs to abuse the lethality changes and then goad them into playing Varus AP support to make game search times better. Not enough people playing support at the moment.