Many opinions were given on the topic of Orcish heights, and after discussing with the Lore team and polling the Orcs, we've come to a decision.
Of course, thanks to the glorious AlpineAl for bringing this issue to light. Without him, I don't know what we would have done. Rulg, brudda.
I. The taller an Orc is, the more his/her posture will be hunched (varying hunch). This can be role-played out at the discretion of the player, but know that Orcs pushing the boundaries of their height are very likely to have some variety of posture problems.
The following heights are if the Orc/Goblin/Olog is standing straight. i.e. an Orc standing at the max of 8ft would probably have a hunch, NOT be hunched at 8ft but really stand taller.
II. Average Goblin height is from 4ft to 6ft, with 6ft being the absolute max.
III. Average Orc height is from 6ft to 8ft, with 8ft being the absolute max.
IV. Average Olog height is from 8ft to 10ft, with 10ft being the absolute max.
Thanks for contributing and reading!
EDIT: Updated in the wiki as well.