In both instances, Kane and Kucherov magically became healthy for Game 1 of the playoffs and helped their teams win the Cup. This season, the Lightning did it again by acquiring Brent Seabrook from Chicago and placing him on LTIR along with the Habs and most notably the Vegas Golden Knights.
Bill Daly was asked about teams using LTIR to help solve their cap crunch, to which he responded, "I see how all 32 of our clubs operate, and I can tell you Tampa would not be the one I'd put at the top of the list." Daly is clearly referring to Vegas in this instance in how they used LTIR to make room to acquire Jack Eichel from the Sabres and then again to allow him to play once he was recovered from his neck surgery.
They constantly rotated players on and off the LTIR such as Rielly Smith, Alec Martinez, Max Pacioretty, Mark Stone, Nolan Patrick and Brayden McNabb to make sure they were cap complaint at various points throughout the season.
Unless the NHLPA agrees to changes to the LTIR protocols and how LTIR affects the cap, which is highly doubtful, there is not much the NHL can do aside from monitoring each team's usage.