I like Oviedo. The folks on my Pirates forums like him. To me, it seems more like the Pirates can't get what they want for Mitch Keller, so Oviedo was simply next to go as he has the least team control. I don't know a ton about Boston's rotation beyond Crochet and Sonny Grey, but I'd be surprised if Oviedo doesn't become your 4 or 5 and possible work up to 3. Don't see why he wouldn't be a regular 2+ WAR starter.
Samaniego was a surprise addition to the 40 man, indicating there was interest in teams nabbing him in Rule 5. He would've been in AAA for us this year, maybe pen depth by summer. Guzman had 5 PAs in A ball, so who knows what he'll be.
From what I've read about Garcia, he Ks a ton. Just about everyone Ks a lot on the Pirates, so we're more interested in the type of K. Is it lack of bat speed/pitch recognition? Is it no plate discipline? Or does he watch called 3rd strikes with the bat on his shoulder? We are K connoisseurs here in Pittsburgh. Our OF sucks, so Garcia will get a spot, probably in LF, which is as big as CF in PNC.
I know nothing about Travieso or what he could bring, but there's a line out the door for all pitching spots for awhile.