It's true that Luger had had discussions through an intermediary, Sting, who he co-owned Gyms with at the time which wasn't illegal, but perhaps a little underhanded on his part. Luger has pretty much stated it got to a couple of weeks before his deal expired and he was asking "Can they do anything for me?" to Sting... Bischoff didn't WANT Luger but did Sting the favour and paid Luger a short, small deal so he could prove himself, which in the main he did and he got a bigger second deal.
He did Summerslam 95 without a deal but as he had no actual match booked I guess Talent Relations didn't see any rush on him, or weren't that bothered to keep him. You can imagine how busy WWE is/Was at that time, a period of readjustment, focus on newer stars like Diesel (ironically) and competition starting down south a week later. They were also in a big signing phase with the WCW rejects like Austin, Foley, Faarooq and Vader all on their way in. It's easy to see how a date to resign Luger slipped by.
It would fall at JR's door as he was the guy in charge of that at the time, but for all we know he could have been telling Vince and being ignored or told to let it go to the wire/play hardball as Luger would "fall into line". Even if it was an edict from Vince the blowback would still go to JR. Perhaps the most interesting thing is that Nash and Hall saw all this and began their own "under the table" negotiations soon after, leading them to give notice at the turn of the year.
Luger and Warrior are two different situations... Luger, like Jarrett before him was quite within his rights to go wherever he pleased as WWE didn't re-sign him. in JJ's case it was a bigger oversight (and I think what killed JR in that role in favour of Johnny Ace) as he held a title and it had already happened with Luger. Jarrett was being asked to job out a title, while not under contract TO A WOMAN, which would damage his stock in WCW. He was quite entitled to ask for more money to compensate for that, especially as barely a year or two had passed since Montreal. Vince didn't NEED JJ to drop that belt to Chyna, there were other ways but he WANTED it and it cost him... Vince NEEDED Warrior at Summerslam 91 and shouldn't have had to pay...but did, knowing the damage if he didn't... Ironically JJ is still "persona non grata" which is harsh but a clear lindicator of how Vince acts if he doesn't get what he wants... imagine messing with what he needs!
For all the JR gets a bum rap from Vince, some MAJOR cock ups happened on his watch contract wise... while he was arguably trying to sign guys Vince didn't particularly want at the time, however great they turned out.
Since these however, it's happened a few times that deals have run down for talents, most notably Christian when he left for TNA. Most have worked out that doing a favour for Vince helps you on the back end... if you hold him up, you're maybe right to do so but in reality hurting yourself later.
Jarrett never came back, Luger never came back and Warrior had problems for all but the last 2 months of his life. Christian did one extra RAW after his deal expired, went to TNA and got a second bite and big pushes... Even if Vince didn't rate him that highly, he remembered he'd been a "good soldier" when he had the chance not to be so it made him more inclined to give him the titles he got when he came back as it would make the fans happy. Punk held Vince up and had him over a barrel to be fair... but as soon as the chance presented itself he was screwed.
Warrior's demands were very ahead of their time... he already wanted control of his name, character outside wrestling etc... they were all part of the letters too. The one thing Vince doesn't like is someone "more ahead of the curve" than him, it's been seen with Warrior, Heyman, Punk, Joey Styles and a few others over the years...creative is good, more creative than Vince? Bad...