Cleric melee ability drops away rapidly from the early 20's. They have plate armour but are not on the same tables for mitigation as a warrior.
While the Lull line enables a cleric to pull from a packed camp the warrior has to choose single-pull targets. Fortunately there are lots of these about. However the cleric is also limited as they really need to pick undead targets and even then will be in trouble.
I was not attempting to solo a cleric much though the levels to 50 except for a while in Katta Graveyard. Here I could fear-kite undead but it was mana intensive and I would have to med after each couple of mobs. And I had to nuke them. Without a snare they take off like a rocket and you get one nuke in on the way out and another on the way back - then fear again. In melee they were hitting me for around 100 while I managed 10's and 20's. Melee was therefore not an option or anything like as safe as fear and nuke.
Root and nuke with Cleric root is a nonsense. It will break on or before the first nuke unless you are very lucky.
I did do a bit of soloing in Lower Guk in my early 50's with maxed 1Hb, Defense, Offense and
Dawnfire and it was still hideously slow and inefficient. Mind you I would have no idea where to try and solo a warrior at that level.
The other problem is that most undead targets don't run which means fighting them 100% of the way. A warrior without this restriction only needs to fight for 80% of the mob's hp.
Once a cleric gets into the summoned proccing hammers things are a little different but by then the mobs are so much tougher and hit so much harder that I'm not sure anyone could solo them in melee.
I do know that as a warrior soloing in late 20's I could do a spire in SK and easily single pull the gnolls. Main thing was to have lots of bandages handy. Now with the increased regen and bind up to 70% it would be easier.
Either will spend a lot of time sitting regenning either hp or mana. Both will be limited on what they can attack (unless you take a DE cleric with the clicky snare)
If challenged to do this and offered the choice of doing it with Warrior or Cleric I think I would choose Warrior. Given the right range of mobs you could still get exp.
Warriors do have to be highly gear-dependent though. A fair bit of time would get spent farming greens for upgrades. The cleric is less gear dependent and can make do with a much lower budget on spells etc. One good thing is the really fast expensive aggro weapons would not be required as there is no risk of losing aggro when you are soloing
.
The other big advantage of the Warrior is that you wouldn't be constantly distracted by people asking you to join groups