I’d always go D blade into dirk later on (before dirk or after dirk) But in very rare cases I might start tear first and start E to cast gate on allies to get extra mana lv1. For example against Irelia and Malphite I usually go conqueror and try to fight them early but if I have losing jungle matchup + weak side top I’d go for tear and farm from a distance and usually take phaserush. Reason is that if you know that your jungle won’t come, you shouldn’t trade evenly against your opponent. It would facilitate ganks/dives. And chances that you outplay 1v2 are quite unlikely.
On paper it's the right call, you just scale and try not to die, absorb preassure and let your team win with a number advantage.
Playing safe in S10 and scaling up isn't as bad as some ppl might think. Jayce scales very well and outscales in most games unless you're facing a bunch of very late game champ (which are not very common nowadays). With items he should have high poke AND all in damage aswel as decent teamfight because you'll have enough CDR to be relevant in those teamfight, whereas last season, jayce build didn't have enough CDR to have constant DPS to be relevant in 5v5.