GMAT is not a key admission factor for HKUST, its important, but not a key or main filtering point. International, cultural diversity is important. Particularly with a keen interest with China because Hong Kong is the gateway to China.
IN terms of Placements, HKUST is stilla young school and growing. The high rankings position in FT and EIU is helping to build the brand in Asia, and competition for places is becoming increasingly competitive. Average salary is very good for Hong Kong, higher than the average Hong Kong Salary. You should not compare average salaries between schools unless youa re referring to the same placement region. Taxes and cost of living are lower in Hong Kong, most students are placed in Hong Kong, so have lower average salaries than USA counterparts who work in the USA, but I would argue they maintain similar lifestyles after you consider Tax, and other cost of living expenses.
Generally speaking, the downturn in the economy have hit all schools hard, including HKUST, although being next to China (which is still growing) has some advantages.