You should play as Melia. She is the best character, but the AI is a touch ropey. 

And yeah, they are hard those enemies. You should be around 70 for the boss there, perhaps a couple levels lower.

I completely failed the Shulk-Seven Heart-to-Heart on the beach. It gave me an achievement for it.

I'm finding difficulty with the questions on a lot of Seven Heart-to-Heart's. Often they hit you over the head with which one is insulting, but with some of these i keep thinking "here they want you to be honest," and... nope. They want you to ego-stoke, or dance around the question. One of them wants you to have Melia outright lie to Riki about how she feels about Shulk, because the truth is the wrong answer there.

Edit: We're positive on the whole "No Heart-to-Heart's become inaccessible" thing, right? Because three pinks are listed for Prison Island, and i'm also seeing a lockout advisory for Prison Island in the upcoming thing.

Yeah. Her Heart-To-Hearts are the most difficult IMO. 

And yes. No Heart-To-Hearts become inaccessible, but it is very hard to get them back. You have to do 2 quests whilst doing a surprise quest after initiating another quest. Which is easy to miss!

But after defeating Gadolt in Agniratha, do NOT go in the teleporter and defeat the next boss. If you do, many more areas become inaccessible. Do all quests in Agniratha now you have the chance!

Have details on that? I quite like the heart-to-heart's, and would rather be able to do all of them this playthrough.

More details on what? That quest?

Find them here:

http://xenoblade.wikia.com/wiki/Broken_Ether_Furnace

Thanks. Yikes, though. Means i'll need to tackle that right before the last set of bosses, won't I?

If you want the last bosses to be competitive, then you'd struggle. You want to be about 80 for the last boss, but a cool 90 or so for that quest. 

Do the final boss, save on a different save after seeing the ending cutscenes, and then grind up quests and Colony 6 to 90.

Very little progress today, mostly grinding and picking up UMs and the odd quest or two. The big takeaway from today is that Reyn-Melia is the last remaining green Affinity in the group.

Time for some Energy Aubergine.

Started the game and stopped it again as I am really disappointed I cannot continue playing with the cool guy who can take on entire armies but have to start with this stupid weak brat that I need to level up before he can win against anything.

Also the in town options of trading/side quests/ buying are so overwhelming that I immediately lost interest.

I found myself in more or less the same position. I often find i have trouble starting any RPG, because there seems to be a big huge world at your fingertips, and you're stuck with this weak little nothing getting killed by rabbits and caterpillars.

Don't worry too much about trading, it's primary use is for getting your hands on rarer collectables that are harder to find on your own later on in the game.

With sidequests, you can go at your own pace. It's better to seek out the ones that yield EXP, however, just don't overdo it. They're good for when you need to grind.

Buying is also overrated, except for Art Books. Always buy Art Books, but everything else you'll get from enemy drops, e.g. better weapons and armor.

My advice: Just follow the story, and then if you find a point where you're forced to grind, enjoy all of the expansive side-stuff then. That's how i've been doing it (though i've been pursuing side stuff becuase i want to get all the Heart-to-Hearts as well)