Just completed this on Classic.
Looooots of reloading involved as I wanted to try out lots of things (plus they kept kicking my ass) but the final mission is much better with the right tech. This time round, I didn't rush it - researched everything and got my final squad to almost all Colonels before going in.
For the two Sectopods I had trouble with last time in the Temple ship I sent in a mind controlled Muton first and a guy with Ghost armour second to get a good position and waste their reaction shots on the Muton. Then my gifted Psionig put up the telekinetic field and the Sectopods missed with all their shots that turn - I love that ability
Finally I disabled them with the snipers and finished them off with the rest of my team. Very satisfying!
In the final room I ran my guys in and kept to the back then my Ghost armoured guy went further in on the top-level to spot everyone, then got my gifted person into position to use the rift on the High Ethereal (it's a guaranteed hit, but it doesn't do him too much damage). Next my guy with the Blaster Launcher hit the High Ethereal with a Shredder rocket (another guaranteed hit, plus I can stay in hiding whilst firing it!). Finally I encountered several bad rolls of the dice as all my men hit the High Ethereal but all shots were deflected but the final headshot from my Sniper got him and it was game over again
I've picked up quite a few achievements on Steam today completing it again, but there are still about 27 I don't have.
I must say that the game was far more satisfying this time around. No idea why the latest patch makes Easy mode easier when Normal was pretty straightforward, but Classic can be satisfyingly/horrifically brutal at times and I look forward to trying it again without reloading - I suspect this will entail lots of running away.
Oh, and my final thought was that I was extremely lucky that I got the request for Plasma Rifles and was able to fulfil that for over 2,000 credits - without that I would have struggled on as my research choices were very poor this time around as I'd not touched laser weapons until much later in the game. The moral of that story is: don't rush for Plasma when Lasers are quicker to obtain... but we all know this from the original too
May your terror missions always be infested with Chrysalids.