Hey Don... this is majorly belated, but oh well. I've thanked you in the past for reviewing albums that I'd requested, so I thought I'd do it again... and ramble on some more.
First of all, another 12! All three requests have been given 12s! I should be glad of my consistency, but damnit, I'm gonna have to suggest something to crack the 13 mark eventually! (I might suggest Alice in Chains' Dirt next time!). And once again, like the previous requests, I've remarked that "I'm not sure how much this album will appeal to you", but you've (thankfully) enjoyed the chosen album. Groovy.
When I first bought Terria, I considered it to be a 14 for me, but... after requesting it, I re-listened to it, and I reckon that a 12 is a pretty fair mark: it's not exactly the most coherent album, and it is a bit... messy. It can wear on you a bit, too. I'd now probably rate it around 12 or 13 myself.
For the most part, I agree with your thoughts: the wall of sound layering thoughout is fantastic to listen to, there's some really soaring and impressive guitar solos, Earth Day is absolutely monstrous and mindblowing, and Devy can really howl, scream and holler, but can also sing normally quite well, too.
On the other hand though, I really like Canada: it's probably the most "commercial" / straight-forward rock song on the album, and I think there's some pretty cool melodies and harmonies throughout it. There's also a rather neat guitar solo mixed underneath everything during the outro, too. I also think the album's "home stretch" of Nobody's Here, Tiny Tears and Stagnant are all excellent: I think Nobody's Here begins a slow build towards the cathartic climax at the end of Tiny Tears and you get a strong finish / reward / pay-off of making it through with Stagnant. And sure, Tiny Tears isn't the most adventurous song, but for me, it's one of the highlights of the album: the song is... I guess, the album's emotional resolution/climax, and the slow build to the song's finale is awesome. Plus, the guitar solo is kinda neat.
Some additional trivia:
Anyway, that's enough from me... thanks for takin' the time to review the album, and glad you enjoyed it.
I also wrote a lengthy overview of the man's other works, so if you're interested, I'll dump it here for you to read.