HO's are big, yes, but posters here are forgetting something - upping the level of your spells/abilities.
If you're new to EQ2 hover your mouse over your spell/ability buttons, and you'll see that most are called "apprentice level 1". Once you get off IoR you can buy "app lvl 2" upgrades to these (in the village where you end up). Rt click and scribe - and tadah, your spell/ability does more (damage, healing, whatever). Yes, your "level one" spell/ability, once upgraded, behaves more like a level 6-8 spell/ability (actually it's better - it's much more mana-efficient, er... power-efficient).
Even better, up your artisan skills to lvl 7 or so, and you can make your own app lvl *3* upgrade (save your money and skip lvl 2 if you have the time to do this). Or buy lvl 3 from player artisans (find a broker npc is one way to find player merchants - see other postings for more details on how to buy from players, or just ask people /ooc in game). Lvl 3 upgrades make that level one spell/ability even better - more like a "lvl 12" or so spell/ability.
Okay, so what is the big deal here? At lvl 8 or 9 my priest was doing, oh, 15 to 17 pts damage with his starter Smite spell w/ app lvl 1. When he upgraded to app lvl 3 damage went up to 27 to 30. This was under lvl 10. As you level up, damage goes up. W/ "app lvl 3" my Smite does over 30 and sometimes 40 at lvl 13.
Same w/ heals. The higher lvl upgrades heal more. Better buffs give better stats. And so on. Heck, you may have just gotten a wicked good lvl 20 damage spell, but if your lvl one nuke is "master lvl" (see more on this below), you're going to have a muuuch better power/damage ratio w/ it (and may well do more damage - I don't have a master - but my app lvl 3 Smite does more damage than my lvl 11-ish cold nuke of app lvl 1 - and for less power).
So, DPS is relative. Not only are people who max the use of HO's going to kill things faster w/ fewer player deaths (HO's do in fact rock - make sure you learn how to do them and encourage any group yer in to use them as often as possible), people who have better upgrades on their spells/skills are going to do much more damage (or heal more, buff better, etc).
So, a Guardian with wicked good upgrades will probably outdamge an Assassin with app lvl 1, all other things being equal.
Well, I need to start wrapping this up here - you really need to search this site and other sites for better info, if you're interested in this. There are Adept lvl 1, 2 and 3 above App lvls - and then there is Master lvl. I *think* adept lvl 1 and master lvl 1 are rare mob drops, and players make adept lvl 2 and/or 3 - but with a very rare harvested/mined ingredient. I don't think anyone is yet making Master lvl spells/abilities - or if they are, there aren't many of them. Master lvl 1 dropped spell/abs currently go on the market for around 10 plat (does anyone yet have 10 plat? I dunno, but these are rare and valuable). App lvl 3, however, are quite affordable (and not all that hard to make if yer willing to skill up in trades). Last night my alt saw a guy selling app lvl 3 priest upgrades for 2 silver, 50 copper.
By the way, "class" is likely *not* to be the big deciding factor in "who gets the sweet groups" in eq2. Your ability to do HO in group correctly AND your spell/ability upgrades likely will ("/ooc Mystic w/ adept 1 heals lfg" > "Templar lfg", e.g. - plus your reputation as a good **** w/ other players). Now sure, if a group needs a healer, it needs a healer. But in the DPS area, again, upgrades and your HO-reputation will count for much.
Best of luck!
PS Ing the basement trade rooms, mage and priest upgrades are made on the desk, fighter upgrades made at chemistry table, scout upgrades made at jewelry table. Again, this is very complex - I only recently learned it - seek out other postings here and on other sites to learn more. Learn as much as you can on upgrads (and HOs). It is "very much" worth it.