In the current storyline that goldberg and lesnar are in right now, yes i does hurt them if owens gets some offense. You're talking about a guy in goldberg that just destroyed lesnar twice on PPV already without lesnar getting any offfense. The same Lesnar that has been destroying everybody in his path suddenly get squash by Goldberg. If you have owens get some offense on goldberg, it makes Lesnar look like less then nothing for not being able to get some offense on goldberg after being push so strong for so long. It makes Goldberg look weak because owens got the better of him for a little bit.
For the mania match to work, you needed Goldberg and Lesnar to look strong going into mania, sadly it meant squashing Owens in the process but again, Owens wasn't hurt at all by this because he can blame of this on Jericho and get his revenge at mania and i think, this actually help his character alot more then if he would have gotten some offense on Goldberg because now, he'S going to be a more vicious character against Jericho and that will elevate the guy even more then getting offense on goldberg before getting squash.
Also, just on a side note, while i do like your exemple, it's not the same situation as what we had here, in the roman reigns vs lesnar match that you use as an exemple, Lesnar was in a feud with Reigns, he didn'T have a side feud with somebody else and using reigns as a stepping stone to get to his main feud, so Reigns could have some offense on Lesnar because their was a reason for the match. The Owens vs goldberg match was just a stepping stone to advance both the Owens/jericho and the goldberg/lesnar feud, so you had to find a way to advance both feud without killing any momentum for everybody. Goldberg needed to look like an unstoppable machine and that match ddid that, Lesnar needed to still look like a beast, and with owens getting squash without offense, he did. Owens needed a reason as to why he got squash without getting any offense, and bringing in jericho to cost him the belt did that and it did help jericho that needed to get some sort of revenge for what Owens did to him at the festival of friendship.
i know that some fans of owens find it unfair that owens lost without offense but like i wrote before, after the way they lay out the matches for mania, it didn'T bother me because it was just part of a bigger picture and after raw, it made Owens look even more like a bad ass just by the pure rage he had about getting squash like that. I think sometimes, some of us in the internet are so much about the actual wrestling side of the matches and forgot that to build a superstars you need to create some great story and at fastlane, that exactly what they did, create a great story that will lead in creating a bigger superstar in owens at the end of all of this.