A elite center by definition makes the players around him better, see Crosby elevating 3rd line guys, etc. Giroux is no longer elite and never will be again no matter who you put on his line. Three years ago G & V were a top line with Raffl at LW. Before that Hartnell.
People just don't want to accept the commonly known fact that most players peak at 26-28, and Giroux has less margin for error as he ages - which is why he's more effective on the PP (more room, more time) than 5x5.
http://www.cbc.ca/news/when-nhl-players-peak-hockey-metrics-1.2646054
http://www.tsn.ca/pinning-down-a-player-s-prime-performance-years-1.388514
James A. Brander, Edward J. Egan, Louisa Yeung. Estimating the effects of age on NHL player performance. Journal of Quantitative Analysis in Sports, 2014; 0 (0) DOI: 10.1515/jqas-2013-0085
The performance of forwards peaks between the ages of 27 and 28. Defensemen are best between 28 and 29, and the performance of goaltenders varies little by age. Players performed close to their peak levels for a number of years before and after their optimal peak: 24 to 32 for forwards and 24 to 34 for defencemen.
Giroux is a 60-65 points center (30-35 ES) who's limited on defense, and no longer can play on the PK. If he was on a $6M contract the next five years there would be no issue, we could carry him at age 33-34 when he's a 40-50 point winger without much pain. But he's likely to underplay his current contract by a significant margin unless the cap takes off, which is unlikely in the new economic environment (see ESPN layoffs, the force that drove sports revenues is now depleted).