I'm surprised there are any solid starting kickers on waivers in a 16 team league. At least a few people will grab a backup in the draft, and there are probably only 25 or so "surething" starting kickers out there..I would drop Sheffler and pickup Mare ASAP.
Carry two kickers all year long just to insure against injury. If your only guy goes down or loses his job (Gostkowski=rookie), then you will be SOL if there is nothing on the WW to use. Seriously, kickers may not be worth a whole damn in fantasy, but if you don't have one to play it can end your season QUICK, they do score points.
In such a large league, don't expect there to be anything just sitting there on the waivers for you to grab at your leisure, you gotta be proactive about it. I would probably drop Pittman to grab a defense as well. Going without a TE for a week isn't the end of the world. But a week without a TE, K, D is almost a guaranteed loss. And I can assure you, there will be plenty of teams out there this year trying to pickup a backup kicker and/or defense on week 6 and 7 when SIX teams are on bye. Don't be left out in the cold..