Dragons scrum half Sarel Pretorius looked to have given the visitors the platform to go on and record a second GUINNESS PRO12 win of the season.
But two scores from stand-in Leinster skipper Isa Nacewa sent them into the interval 20-10 ahead and debut tries in the GUINNESS PRO12 for Gary Ringrose and Cathal Marsh in the final quarter helped their side record move up to fifth.
Fergus McFadden starred as he kicked an impressive six from six - as Nacewa also added a conversion - as Leinster recorded their second GUINNESS PRO12 win of the season.
The Irish side have been one of those affected by a high number of absentees at the World Cup but Jones believes the Dragons' poor display meant they could have had even more away and still won.
"Leinster had 16 Ireland players missing and it didn't really matter. They could have had 50 away at the World Cup because our standards were so poor," Jones said.
"It was a very bad day at the office and we simply weren't accurate in anything we did.
"We need to knuckle down, get our selection right and get people working harder for the cause.
"In sport some days it will happen for you and others it won't but we need to be tighter than that. It just wasn't good enough, but we are confident that we can turn this around for Glasgow.
"After that we don't want another week off but that's the way it goes.
"We are trying to move forward and need games to do that. Unfortunately we don't have them at the moment."
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