Crit is the lowest valued stat regardless for Restoration. The only question is between Haste and Mastery. Most people go for Haste to get the 9th tick threshold of Wild Growth and Efflorescence as that is a very considerable throughput increase. It depends on raid buffs where it will fall for you (2005 with just 5% spell haste buff, 1573 if you also have Dark Intent). Mastery will be better between breakpoints. Also if you're exclusively tank healing mastery will trend to be better because you simply aren't casting as many healing over time abilities (if you never cast Wild Growth, you get no benefit from its haste breakpoint). Because most druids aren't exclusively tank healers, they tend to favor haste as it has significant impact on the abilities they use as a raid healer when they reach these breakpoints.
Mana shouldn't be much of a concern regardless at this point, however one of the core reasons you don't have mana issues is because your haste is extremely low, you're regenerating a lot of mana in the time it takes for you to finish casting a spell.
Your meta gem isn't ideal, you really should be using an Burning Shadowspirit Diamond. You said it yourself, you don't have mana issues.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.