Try the survivor's Curse skill. It can be cast repeatedly on a target to greatly lower their resistances, then followed up with elemental or poison damage, or skills that can be blocked by spiritual resistance.

The Burning Wall skill can also be very effective, even at level 1, with good timing and coordination (for best effect, you need to cast the spell and run in a tight circle around a target, or group, and it can also be used to slow and damage opponents trying to follow you). In my first game I found a spell book in Mardaneus' house, and it came in handy twice (for the spider at the bottom of the catacombs and the first heavy orc south of Aleroth in a large group), though I never used it after that.

If you've been collecting trap material, or happen to have some in recent loot, the survivor's Deadly Gift skill is good at level 1, with scorpion traps.

Check back with Kroxy periodically for potions (particularly restoration potions), equipment upgrades, spell books, etc; maybe also check the orc at the start of the wastelands (though he is more expensive). I don't recall if there is any hay/straw in the wastelands to make a place to sleep, but there are a few beds you can use (including in Kroxy's house) if you leave a teleporter pyramid beside one.
Do you have gold charms and equipment with open charm slots (to permanently add a bonus to the equipment)? The dragon armour set pieces are potentially some of the best pieces of the respective equipment types you're likely to find, but they are not essential. You may be able to find or buy stuff of comparable quality.

I was level 45 when I did the Blessing Ceremony, so moving to the wastelands brought me up to 50, and I got to 53 by the end of the game (skipped some of the mobs in the Black Ring dungeon); the average end level range is from the mid 40s to the low 50s.
I didn't have a problem with the group of dragon riders, even spending most of the fight frozen.
Clearing more of the wastelands to level should help somewhat.

Josephine is arguably the toughest opponent in the game (though if you attack right away and interrupt her summoning, she keeps trying to summon, and doesn't move on to her Blind + Hell Spikes combo).
The passive Stun skill helps with interrupting her. If you get blinded, you can use a shadow potion to wait out the effect, or switch to area effect skills that do not need a target (like Hell Spikes, which do physical damage, so can not be resisted... though as a warrior you probably don't have them at level 4 or 5, which is required to be really effective).

The techniques that work against Josephine should help with any strong opponent: Chasing Josie...

That's fine; I didn't care about reputation even when it was listed (before GOG implemented 'Developer' accounts). ;)
EDIT: Actually, the topic wasn't posted as a question, so AFAIK can not be marked as solved, anyway.

Yes, Josephine does do the same thing in the second fight (that is what I was referring to). I was actually looking forward to the second fight, with the rest of the wastelands being relatively easy (at level 53 with good equipment), but (with Stun maxed) all I did was run up and hit her until she died, never getting past starting to summon before being interrupted.
Moriendor (who uses a similar tactic) put up more of a fight, blinding my character and doing some damage with Hell Spikes; I used a minor restoration potion and withdrew into the hallway to let the blind effect wear off, and was able to quickly finish him when he came after me.

Spiritual Arrows reduce hit points, if they hit, but do spiritual based damage rather than physical.
Ghosts and undead tend to have high spiritual resistances (level 21 zombies and steel skeletons in Iona's dungeon about 36, for example, and level 29 and 31 ghosts, liche and mummies in the council hall 100).

Congratulations.

Reading the first post I was going to ask if you tried Burning Wall.
Also, it isn't needed now, but iZakaroN's SaveEditor could undo the points you put into Enchant Weapon. Using a hotkey to drink potions will not interrupt your standard attacks, or cause a delay when right clicking to use skills or spells. Open the potion menu, hover the mouse cursor over the minor or regular restoration potion stack, and press a function key (F1-F10, F12) to assign a hotkey.