I found scrolls to be a huge problem right up until chapter 6. The game just doesn't have a lot of them as treasure, and the one merchant who actually stocks scrolls is incredibly condescending and refuses to sell you anything above 2nd level spells until much later in the game. He's got a good selection, but it's all low-level stuff. For a 2-man party with all the extra XP that comes with it, his stock is going to be completely beneath you.

Your wizard is going to be starved for scrolls right up until chapter 6, where the game finally drops as a suitable treasure-trove of high-level scrolls on your character. Once you reach Heart of Winter you'll be fine, but the campaign leading up to it is very sparse in magical scrolls.

There's a vendor in Kuldahar (a wizard named Orrick) that, as noted, has a number of low level scrolls. When you start chapter 2, his stock changes, so he carries a selection of higher level spells after that. Still, it's limited, and will be very much so considering the XP gain you'll be experiencing and the level your mage will likely be at. Better than nothing though.

There's also a vendor in Dorn's Deep that sells some higher level spells, but again, a limited selection. I'm not sure if this is the one that Davin was referencing, but he's pretty condescending, so I think it may be.

Finally, you'll find a number of scrolls as treasure in various dungeons. Overall, I think you'll find you'll have enough spells to keep you going, but you're not going to have everything you'd likely want. Which is likely a good thing as it makes it all the sweeter when you do find a new scroll that you really want.

Nah, I was talking about Orrick. He's pretty condescending, saying outright that you're beneath him and he refuses to sell you anything particularly advanced.

The big treasure trove in chapter 6 is when you fight the Drow Sorcerer and get to loot his library. Lots of great scrolls here; this was the first time I felt my wizard actually had a spellbook sufficient for his level. Playing on very hard (x2 experience) I found the treasure completely insufficient in this category. My single-class mage was being held back for pretty much the entire game because he couldn't find any scroll with which to fill his higher level spell slots.

Yeah, I understand what you're saying. I'm in a similar boat, just having reached Wormtooth Glacier with my party and only just shortly earlier was I able to have a selection of a few level 5 spells. But that being said, this is kind of what I meant. Sure, if you have level 6 or higher slots it sucks to not find anything to slot in there (and you won't until the area you mention), but you really do appreciate another level 5 spell when you find it. I still find my mage and Bard have lots to do with the spells they have.