You really shouldn't skip or even delay Trebuchet, especially not for God's Strength.
I believe Trebuchet hits DGs for 250, so with good armor that's still going to be 150+ damage and it fires every 5 seconds. Most of the time you'll be hitting for at 180+, it has small radius splash damage against creeps, and it strikes structures for 500. The ability targets DGs first, towers second, and others third, so it will lock onto a hero in a busy fight unless it's already locked onto a tower before the hero enters into range (which is a good thing, since it lets you siege without leaving or extending your tower farm).
Generally you'll hit a DG 3-4 times between every hammer slam up until very late game when both you and your enemy are ballsy enough to stand in melee range through the full duration of slam's (or possibly boulder's) cooldown. By that point you should have maxed out hammer slam regardless though.
There's virtually no other ability that will gives you that kind of mileage, generally it's even better than taking the next rank of Hammer Slam, though of course it's not the on-command splash damage hammer provides. The notion of taking God's Strength, which hits for only 50 per hit pre-armor (so about 30 per swing with decent armor) every 2 seconds or so and only when in melee range, is ridiculous.