In the Ruins of Symbaroum (RoS) book every race, save goblins, and class has a d8 HD. And because players are given the option of using the classes HD instead of their origin HD a goblin mystic would have very similar hitpoints to a troll warrior, that doesn't feel quite right. The Troll and Ogre get slightly more hitpoints, 1 on average, than other origins but that doesn't feel like enough. Have you added any house rules to add greater hitpoint variation?
Hey! Just seeing this now, but wanted to respond.
Using Class hit points / Hit Dice instead of Origin is an option,but as specified on page 44 of the Player's Guide
, the default is to use Origin, not Class. The Class Hit Die is there only for those players who really want play that way as a group (i.e. not an individual picking to use the Class HD, but the entire group needs to pick) or use a class (like Captain) in a regular 5e game. The entire system is built around Origin Hit Dice and a group would want to think very seriously about making that change as a whole, and think more about Goblins, Ogres, and Trolls.
As an incidental by-the-by, we did try very hard to have Ogres and Trolls be Large, but too many things break (grappling is a big one). So if you do go to Class Hit Dice, their current traits and Origin Feats are our best. attempt at meeting in the middle (as is Survival Instinct for Goblins), and will need adjustments.