Standard? Yes. Sketchy? No. Annoying? Absolutely.
Nothing really ethically wrong with streaming as it's well within the rules when the rules allow for it, but there are certainly things that can be done to stop it in future seasons if you and the majority of your league mates are willing - if it's roto, you can slap either weekly lineup changes or an IP limit and that will pretty much solve the problem; If it's h2h, you could also go weekly lineups (though I'm not personally a big of a fan of this in h2h, I've played leagues like this and it's worked pretty well) or have something like max IP/week.
Gotta tough it out this year though, and just know that when you're facing a streamer it's your week to maybe go all RP and take saves (and/or holds), ERA and WHIP - let him chase wins and Ks all he wants as it will blow up in his face plenty of times anyway - just don't get sucked into a stream fest or you might end up dropping guys you don't want to drop and losing 5-0 or 6-0 in the pitching cats anyway