I'm actually playing my third game with my warrior (lv.24), reaching the 14th floor with many struggles. Am I mistaking something? It's hard to kill those demons, and I have to keep on using the teleport scroll to heal myself and buy potions.

Well, the game is not supposed to be easy. :-)

Some tips that might help:
* Warriors need all the dexterity and +xx% to hit they can get.
* You should be using a sword + shield combo.
* If you find equipment with +magic, hang onto it and use it (only) to read spell books.
** The most important spells for warriors are Healing and Teleport.
** Stone Curse, Fire Wall and Chain Lightning are helpful when you can't just melee everything coming at you.
** Town Portal, Telekinesis and Guardian (for scouting) are nice utility.
** The other spells are rarely useful for warriors.
* If you can't beat the Hell (13-16) levels yet, you may still create a new game on Nightmare difficulty and do the Church and Catacombs levels there. They're easier than Normal/Hell.
* You might want to read Bolty's High Level Warrior Guide for an idea of how a late-game Warrior plays. Especially the parts about movement and positioning. Or don't read it and figure things out on your own. :-)

And practice the most important D1 tactic:
* Only advance one step at a time. See if anything comes at you. If so, take them out before advancing further. Getting swarmed means getting killed.

I played as a warrior too. Feranur makes a lot of good points and even brought up some things I didn't know, but I'd like to add from my own personal experience too. I managed to beat the game at level 26 and have beat the original a couple times before at lower levels.

* Keep a town portal active before you go into the fray. That way you don't have to worry about casting the spell and panicking/messing up. You'll risk wasting mana, but towards endgame it's better.
* Armor Class is incredibly useful towards the end. If you can find platemail with +100% or more armour, get it. Same with the shield, it really adds up.
* Ele Res is pretty easy to max out, so do it. Combined with a high AC, it mostly becomes a race of "who can wear the other one down first?"
* I agree with Feranur's point on dexterity and having a good To-Hit. I got lucky towards end-game and picked up a sword with +49% hit & +116% damage + 7 damage added and ended up beating Diablo with a 122% To-Hit, but if you get the sidequest to get Griswold's blade, do it. It's one of the best swords in the game, which leads me to my next point.
* Do all the sidequests you can. The rewards are largely valuable. Granted there is some random assignment ( see here ), there are some particularly good warrior items (the Veil of Steel is especially good). Worst case scenario, you can sell it and get a nice amount of currency.
* Items with +all attributes are very useful, but they should come third to maxing out your Ele Res and your ToHit% (though keep in mind +all = +dex = +tohit, so experiment and find a middle ground).
* If you can get a ring or armor with Faster/Fastest hit recovery, I would consider keeping one in your inventory so you don't get stunlocked. This caused a huge amount of frustration in my early-game, but once I got an item with faster hit recovery, it got easier.
* If you do decide to pursue magic, reading multiple copies of a spellbook increases the spell's level, and one of the consequences of that is reduced spell cost.
* 1h + shield > 2h all the way in this game.

Fast(er/est) hit recovery can be nice if you get stunned frequently, but the better solution is to stop getting stunned so much.

- Keep your Armor Class up.
- Get your chance-to-block as high as you can. Dexterity helps, so +all or +dexterity items are useful here. Put every level-up statistic point you can into Dexterity until it maxes out.
- Keep a shield equipped.
- Remember that you can only block if you are idle or attacking. Any other action prohibits blocking, so do not walk or cast a spell if you are about to be hit (unless you are sure you can finish the action in time). Feel free to swing your weapon at the enemy. Your character will interrupt his own attack to block the enemy's strike, if needed.
-- Notably, if you are busy blocking one attack, you cannot block another. Try to avoid having multiple enemies land blows at the same time, as this may lead to getting stunned when you fail to block the second attack. Being stunned also prohibits blocking, so you could quickly go from blocking every attack to being stunned by every attack. Fortunately, warrior block animations are quite fast, so you need to be quite unlucky to be hit while you are busy blocking. It can happen if you get swarmed though, especially with fast attack enemies like Lightning Demons.
- As a warrior, the Fast Block special ability (shields "of blocking", Holy Defender, and Stormshield) is pointless. Warriors already block at the speed that Fast Block would give you, so you should not count Fast Block as a perk when evaluating an item. Rogues and Sorcerors block faster with it than without it, though.