1) Yes, I play at high levels. It's actually my preferred area of play. =)
2) Yes, I would use Polar Ray. Because I can use Twin Spell Split Ray on Polar Ray and not on the Orb spells (because as much as they are like rays, they simply aren't). That's not to say I'd never used Orbs. But the question is a) will I be facing creatures with SR/spell immunity and b) how many. In the absence of a), I'll be using Polar Ray. If they have spell immunity, I'll use the orb. If they have spell resistance, it depends on b) which i'll get to later.
3) I'm not saying that an attack roll isn't better than a saving throw. But if you've ever played D&D, you'll also know how you'll hit on a roll of 5 and above yet you managed to roll 4,3,2, and even the dreaded 1. And again, once they're in melee and firing into melee penalties and cover applies, I'm more hesitant to fire a ray (especially when there's a chance I'll hit an ally). If the dragon in the example used the spell Scintillating Scales which turns their nat armor into a deflection bonus (dragons can cast spells too!), I wouldn't be hitting them in the first place unless I rolled a 20.
4) The dragon example is biased towards the Orb user in the sense that it's a single target. If I were facing multiple opponents (even if they have SR), I'll most likely still be using a Delayed Blast Fireball or Chain Lightning (plus whatever metamagic feat). As I mentioned earlier in the thread, the strength of Evocation in my opinion is its ability to tackle multiple foes. If I were facing single targets, I could depend on other schools (Enchantment, Necromancy).
5) In the case of the dragon, honestly, I wouldn't be using either Evocation or Conjuration. If I was of nongood alignment, I'd be casting a Split Ray Twinned Maximixed (Rod) Enervation. The dragon actually has a lower SR for its CR. With spell penetration I have a good chance of penetrating the SR (I'd probably even invest in an item that boosts my caster level or those that helps beat SR). If various books are allowed, I'd cast Assay Resistance in the first place to give me a +10 bonus to the caster level check. Actually optimally speaking, I'd never use Meteor Swarm. It's not as cost efficient as I'd like it to be. I'd honestly actually use Polar Ray (plus whatever metamagic) on it or a lower-level evocation spell (delayed blast, etc.).