Andor's Trail

Is there any particular reason why the number of potion sold by potion sellers or priests are very limited? You can use up 10 health potions in very short time. Even though I can simply go to sleep to regenerate the potions in the store again, don't think that's quite effective. Again, if that's on purpose, what's the philosophy or reason behind doing it this way?

It's to stop you from buying an absurd number of potions in one go, and becoming a potion junkie
You can also refresh a shop by just leaving the map for a few minutes.

Minor potion of speed! I need more! Please, give me more. I need, need, need them

So, we need to waste time to let the store have the potions again. I don't think that's a good game play. I've never played any RPG that is so limited in the amount of potions sold by NPCs, even when potions ae available through different means, such as craftings etc. But J guess I'll just have to live with it.

If you are that reliant on health potions, then you are missing out on alternative strategies. Food? Regeneration skill?

I think numbers are perfectly fine. There's meat which helps to regenerate health for free, and I use it often early in the game when I am saving money to buy equipments.

Corpse eater, regen, rapier of lifesteal, necklace of the undead.
Potions people actually buy potions? A few bonemeal to make it to Lodar sure.

Yes, I do use big pots in high levels. For low levels I do use meat and the med pots farming from skeletons and the like.

I consider one level of the Regeneration skill mandatory. I also use a lot of high regeneration food (meat early, because that's all you can get, but there are much better foods).

The Increased fortitude skill also helps, because the more HP you have, the less you need to worry about them being depleted. You should have at least one level of this.

Corpse eater feels a better investment than regeneration from a long term perspective.

In short term playthrough, DR items are a better investment early on. There are some great ones available early in the game that can protect the player from damage upto 6 HP, which covers maximum number of monsters in and around starting areas.