I can understand they are a race bred for war, and yet even if they are not goblins (i have read the companion and strong bones do no mean strong muscles... the rest is mostly about the giaks having resistance to heat and poison, and to me that dead fellow is not an herculean machine of brutal mayhem) I still consider a value of 18 in strenght a bit exagerated. Let's say the average strenght of a normal human stands between 10-11. An above average human would have 12-13, a fairly strong human would have 14-15... you get the picture. It then means that an exeptionally strong individual would have the value of 18. To me it is totally irrational to have a whole race with an average strenght of 18 unless that race is giantish or particularly squat(more large then tall).A value of 18 means a +4 in damage and most adventurers on Magnamund have already killed a giak or two without having to be wounded by a 1d4+4 hit from a butterknife-wielding grey-skinned slave of the darklords. I could settle for a 14 or a 15 and even then I still think a 13 is totally appropriate for the giaks for it means they are strong, above the average human...
Let's quote the companion : "they were small, squat and grey-skinned..." By small it means small... No small scum, should they be spawn of the darklords, can have a 18 in strenght, statistically and physically... Well those are my thoughts... IMC Giaks are small, brutish and cunning... They are not some Uruk-Ai crossbreed who run away in fear when Banedon hits them with some lightning spell... They are cannonfodder and I think they should be considered as such...