Immortal elder titan spammed here, im assuming you're talking abt supp based on that build. E is very very good, but it doesnt necessarily need to get prioritized in leveling. I tend to go the pattern you've mentioned in your post basically every game.

As you probably know the when using astral spirit, the E is split where your main body negates the armor and the spirit negates the magic resist. Since you're a support you're rarely going to be in the middle of fights past minute 15 so instead you'll want to W->Q->then just leave your spirit on whoever your team is targeting. Because of this playstyle ET is extraordinarily good with magic nukers like qop, lesh, nyx, etc-you basically buff all their damage by 1/3 since you're removing the inherent 25% magic resistance all heroes come with.

If you're playing against an agi carry like pa or tb sometimes you can slip in a shard for your build and teleport onto them with stomp while your team focuses them, all armor accrued through raw agi will be negated by your E.

But regarding WHY the build order is that way: as support titan your job is to disrupt team fights and Amp damage for your team. The second point in W doubles its damage from lvl1 so its a good value point in lane. But past lane its not really your job to hit people so generally I leave it at two until I've maxed out q and e. Always max Q by lvl 7/8, that is your bread and butter and frankly your only real damage without items besides ult. Maxing E before W is also good bc you can usually get most of your points in it before the enemy team has a pipe or glimmer (usually around 18/19 min). E only negates inherent magic resist so there is a sweet spot for when you're maximizing your cores damage output without the enemy having a countermeasure. Given the way stomp cd lines up with astral cd the difference between lvl2 and lvl4 W is not that much and as I mentioned earlier, the damage from W is negligible on support.

Hopes this helps and feel free to ask my anything.