Gronk's cap hit for 2017 is only 8th highest in the league for TEs at $6.75M. His production per game in 2016 was still better than nearly all starting TEs in the league.
Until he got injured, he was leading the league in yards per catch for ALL pass-catchers (21.6), WRs included, and maintained a 66% catch rate, even at that depth of target. Typical catch rates for the top "deep threat" pass catchers is 55%-60%.
OTOH, Gronk's cap hit for 2018 & 2019 ($11M & $12M) would put him at #1, ... $2M above anyone else in 2019. IDK how much of those salaries may or may not be guaranteed for injury. If they're not, the Pats are only paying for what they get out of him.
Gronk turns 28 this May (a day after I turn 65), so he'll be 29 after the 2018 draft and 30 going into his contract season. I'd guess that significant decisions will be made about his future with the Pats at the end of 2017 based on his performance, contributions and health.
If he's ready to go for the start of 2017, stays healthy and produces well, the Pats could extend him to reduce his cap hits, but he'll be difficult to trade since his cap hits with his new team would still be $9M & $10M respectively.
If he doesn't stay healthy and/or doesn't produce well this season, then a straight up salary reduction, or ...?
Anyway, limiting Gronk to 6-8 targets per game and cutting out those 10-15 target games wouldn't be exactly coddling him. Six tgts/game (~4 catches/game) would still be about 64 catches per season and probably around 1000 yards. Heck, he had 25 catches in 8 games in 2016 and still produced 540 yards.