Hey, there. Let me see if I can help you out of the jams.
1) Yes, it is perfectly fine to do nothing on your turn. This is especially true if you start your turn with an empty hand or if the cards you do have are not helpful given the current situation (i.e. you are playing a low strength caster and you don't have any combat spells in hand). Just remember that the steps of your turn still technically happen (i.e. you still have a move step even if you don't move), therefore you will still need to apply any effects that happen during those steps. For example, if your location deals you damage at the start of your explore step, you will take that damage regardless of whether or not your explore.
2) No, that seems to be a house rule your friend made up.
3) No, you can use any character with any set, and yes, you would start fresh with no feats, only basic cards, etc.
4) To my knowledge, you wouldn't have to remove any character from the base set. I am not aware of any rule that says you can't have multiple versions of the same character being played at the same time. That is, you could play the class deck version of Alahazra while someone else in your group plays the Mummy's Mask version.
5) You use the role card that comes with the version of the character you are playing. If you use the Skull and Shackles version of Alahazra, you use the role card from Skull and Shackles. If you use the Class Deck version of Alahazra, you use the role card that came with the class deck, etc.
I'll echo the sentiment here and elsewhere by saying that I'm not a big fan of bane spreaders in general as they really slow down the game with larger groups and can adversely affect support oriented characters (losing a bunch of cards on another characters turn isn't the best feeling).
I feel like there should be some kind of check to defeat that would allow the party to avoid the summoned banes, such as a stealth/perception check. That would make thematic sense as a stealthy or perceptive character would be able to sneak past a horde of demons or skeletons, etc.
This would give a party a broader set of tactics for dealing with this type of barrier and would make the stealth/perception skills more useful than they currently seem to be as neither check seems to come up all that often, at least in Wrath.
I've played through all 3 APs with each character as well as about half of the class deck characters, and I have to say that it's a real testament to the designers that each and every character I've played has been really good at what they are designed to do.
Of the Skulls and Shackles AP characters, I personally had the most fun with Alahazra, Damiel, Seltyiel, Feiya.
From the class decks, I'd say Harsk, Seoni, Kyra, Zarlova, and Siwar are all good choices.
I'm currently playing though the Season of the Shackles campaign with Amiri, Sajan, Amaryllis, and Lini and it's going quite well.
Really though, as long as you have a good mix of skills and powers, you should be able to take just about anyone through the AP.
I don't think scouting is overpowered at all. I find it to be an essential part of the game. If anything, there should be more mechanics like scouting that allow players to tactically circumvent the more devastating effects that crop up throughout the game.
Otherwise, the game can become incredibly frustrating due to all of the random bs that gets thrown in (i.e. Demonic Horde, Arboreal Blight, Army barriers, etc.).
As far as I can tell, the cards are a mix of boons from Runelords, Skull and Shackles, and Wrath. There are a few cards that seem to be unique to each class deck, but those may end up appearing in the Wrath set later (or another set that hasn't come out yet).
The characters themselves are all unique, though. Even a character like Valeros, who was appears in both Runelords and Skull and Shackles, gets a unique build in his class deck version.
Having played both of those scenarios yesterday, I will say that there was a bit of audible swearing when Aribundi failed to roll a 12 on 2d8+6 on 3 of 4 consecutive encounters of said henchman...
...I hope that the designers avoid these "everybody fights a thing" barriers in the future for the reasons stated in this thread. They didn't have them is S&S and I think the game was better for it.
If these barriers must continue to be a thing, they should at make it so that not everyone needs to pass their check or that the summons are limited to one location (or perhaps only open locations).
Maybe something along the lines of: "When you attempt (□ or another character at your location attempts) to defeat a barrier that has the Skirmish or the Task trait, that character may use her Diplomacy skill in place of any listed skill for the check."
From the card of a certain smooth talking Bard... ;)
I'm in agreement with Joshua. It feels weird that scenario 2 out of 35 would be so difficult and outside the norm of what most scenarios play like. I would think that the idea would be to give players a few scenarios to get used to their characters and the various game mechanics before throwing in such a curve ball.
I'm hoping that the Carnivorous Stump is intended to allow players to attempt to close locations.
I think you'd be okay, depending on who the other two characters are. Imrijka's high strength makes her ideal for longbows and such. There seem to be enough ranged weapons to go around. Also, you can't go wrong with extra cures.
As an aside, I like to think that Imrijka's strength based ranged skill means that she just beats her foes with her bows.