Det, Crit and SkS don't add any STR or anything. They each have their own effect, as described, which directly/indirectly increase dps.

Det increases damage done, physical or magical, as well as HP healed. Crit increases your crit rate. SkS reduces your GCD and cast time for casters.

The stat weights you see floating around are a measure of how much 1 point in these stats increases your DPS relative to 1 point of STR. For example, 1 point of Crit will increase your crit rate a small amount, which will result in increased dps due to an extra Crit over a certain duration. The weight represents how much this theoretical increase is compared to the direct increase granted by a single point of STR.