In a world I’m designing, one of the eldest extant intelligent species is the Trolls. These are not D&D trolls, but something else. I have a number of basic characteristics for these beings, and am wondering whether these characteristics necessarily imply anything remarkable about their physiology.
Note: Assume that everything is Earth-like unless otherwise stated.
The Basics of Trolls
Trolls are about 3m tall, and weigh about 300-400kg.
Their bodies are mostly covered in a thick, coarse hair. This hair, like that of wolverines on Earth (gulo luscus, gulo gulo) naturally inhibits ice formation.
They are viviparous and mammalian. They are also marsupials, at least in the non-technical sense that their infants are carried and suckled in a pouch.
Trolls live an average of 200 years, barring major injury.
They live principally in a large system of cold fens and moors. During the warm months, the weather is not unlike that of northern Scotland: cool and moist. During the cold months, temperatures rarely rise much above 0C except at midday, and nighttime temperatures are commonly around -15C.
Their diet consists primarily of vegetable matter, though they scrounge a certain amount of protein from insects and carrion. They do not normally hunt and eat other animals.
Trolls are immensely strong by comparison to humans, on the order of gorillas.
They are extremely durable: not only are they difficult to hurt in the first place, but they heal quite rapidly and consistently. They are not significantly prone to major disease.
Based on these characteristics, I imagine that a certain amount can be inferred at once regarding their physiology. However, I know very little about animal biology. Specifically:
Given these characteristics, are there other necessary or extremely likely qualities that would be remarkable? (By “remarkable,” I mean something that is not usually the case for all mammals and would probably get mentioned in a fourth-grade book on animals, but that I have not mentioned here.)
Are there any serious objections to animals like these trolls existing? (That is, some of these characteristics appear mutually contradictory, requiring some other as-yet unstated quality to explain—or perhaps requiring me to eliminate something.)