I honestly believe Nebula is the god-tier armor here, it grants as much HP regen as Spectre granted lifesteal, it WORKS on multiplayer (unlike Spectre which pretty much lets everyone die as the life steal cap is not quite enough to keep people alive) and also buffs mana regen and damage by a crazy amount. It truly outclasses what every other armor can do, except Stardust, which has the most unique effect of all armors, but let's be honest, it's barely any useful.
I don't personally like Solar too much, while it's cool it has the effects of every other end-game melee armor mixed together (Turtle, Beetle Scale and Shell), I really dont like the fact it is inferior to both Beetle Scale in terms of DPS and Shell in terms of damage reduction. I do like the recent buff however, which makes it so you don't consume shield charges to simply dash away from danger.
While Vortex sounds pretty much the same as Shroomite, I heard it lets you hide from enemies EVEN when you are the only target around, which makes the set bonus actually incredibly useful. I haven't tried it myself however, but using it, rangers can easily out-DPS any other damage class in the game. When it comes to glass-cannons I would honestly put it on god tiers above Nebula.
I know people talk
about Stardust but I can't really say how bad it is as I've never used it myself.
I agree that Nebula is god-tier. The pickups are amazing when you're alone, and they're amazing to give to friends, too.
It's true that Vortex affords huge DPS numbers, as one night of Pumpkin Moon will readily prove, but DPS counter readings definitely aren't everything and can even be deceptive. For example, piercing bullets and arrows can give enemies 1/6th of a second invincibility frames, which is why my friend and I finished Pumpkin Moon with ~51,000 points twice: Once while I was wearing Nebula with Lunar Flare and he was wearing Solar with Star Wrath,
and again with both of us wearing Vortex, min-maxed accessories, Unreal SDMGs, Luminite Bullets, stealthed the entire time. It's not hard to deal damage in Pumpkin Moon, either. At wave 15, the enemies get right on top of you and all you have to do is hold down LMB to pierce all of them. We each got up to 30,000 DPS on the meter.
Actually, strictly speaking, Last Prism can theoretically out-damage Phantasm and SDMG
combined, especially with full Nebula pickups. This supports the notion that big numbers on a meter don't tell the whole story of what actually happens in practice.
Virtually every gun and bow in the game requires line of sight to the target and is stopped by blocks, except the Piranha Gun or if Chlorophyte bullets are used (and their ability to verve around blocks is quite limited). Many also require very good aim to use to their fullest potential, which, while it's great to reward careful aim, not everyone has in abundance.
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The issue with the Stardust Guardian is that it sits in one spot on a solid block and has an aggro radius of about ten blocks. This works fine with, say, Illuminant Slimes, Illuminant Bats, and Chaos Elementals; the Guardian will attract their attention very well indeed, because those enemies are slow.
It doesn't work worth a crap on celestial pillar enemies no matter where you put it, because 1.) many of them fly every which way; 2.) the ones that don't fly, like solar pillar infantry, blast across the screen (and through blocks) so quickly that the guardian can't snag them; and 3.) there are a lot of them.
The Guardian can't tank Moon Lord or any of the eyes, either. So basically, the endgame Summoner set bonus—which you can't even get until you defeat the pillars and the Moon Lord—doesn't actually help at all with subsequent pillar or Moon Lord fights.