When you get Torpor at level 60, you will be regenerating at 300 HP per tick. This means the extra 8 HP you get as a Troll while standing (you RARELY sit as a 60 shaman with Torpor) is barely noticeable. I am not saying extra regeneration is useless when you have Torpor, but it becomes MUCH less significant.
This is why you rarely see level 60 Torpor Shamans running around with
https://wiki.project1999.com/Fungus_Covered_Scale_Tunic . The extra regeneration becomes much less noticeable. Level 60 Torpor Shamans (myself included) tend to prefer
https://wiki.project1999.com/Chestplate_of_Vindication for the high HP and high resists. If those Shamans are willing to lose an extra 13 HP regeneration per tick, they are certainly willing to lose an extra 8 HP regeneration per tick.
Frontal Stun Immunity, however, can be a lifesaver. When you are fighting a super tough mob, you will only have a few minutes to get control of the situation, or die. An untimely interrupt when casting Slow, or Torpor, could be the difference between life and death.
Lets say you only have 3 minutes to gain control of a situation or die, for example. that extra 8 HP regeneration from being a Troll will net you a measly 240 HP over 3 minutes. That is 1-2 hits from a tough mob. Not a lot of benefit. Getting less interrupts on a Torpor or Slow, however, means you have a higher chance of getting control of the situation. If you have to waste an extra 15 seconds trying to slow the mob due to interrupts, you are losing WAY more than 240 HP.
This is why Ogres tend to be considered the best Shaman race. Frontal Stun Immunity is something you cannot get on gear, and regeneration becomes much less desirable at 60 with Torpor.
EDIT: In terms of your snare question, the necklace is not that great. It lasts 6 ticks, and the snare is so bad the mob needs to be at 10% to stop running, instead of the usual 20%. Not to say it is useless, but it is definitely not as good as it would need to be to justify rolling a Troll over an Ogre. If you really want snare on an Ogre, you can get
https://wiki.project1999.com/Spear_of_Constriction. Removed Anklesmasher, thought it was Shaman usable for some reason.