The rod's attack rating is important, not just the properties it has. Ice is by far the most useful in most situations, but there are times when fire is indispensible as well. I still hate lightning.
(This is just an addendum to what you've already said):
The rod's attack rating is it's most important aspect generally. The only time it's not is if a new rod has a similar min/max as your last--even if it's somewhat less--but it has really good mods such as higher elemental damage, damage, +%damage if spell is repeated as well as +%damage for +%mana. Typically it's just better to go for a rod or wand with a significantly larger raw damage than what you're coming from, even if it doesn't have any good mods on it. One mod to stay away from however is the -%damage for -%mana. That mod is only useful during the levels you won't actually see it at. Then there's the specialty rods for when you're leveling up such as +23% vs demons, humans, nature etc. You would just switch to the bag that had that rod, along with other gear with the same mod for specific dungeons and bosses.
The best way to check how much of a difference a rod or wand is in damage wise is to simply beat up on Rannie. Just make sure one does not have a bonus against humans if the other does not, because it will skew the results. Also, if you're using a rod that has +%damage if spell is repeated on it, you'll have to either drastically pause between each shot, or simply cast another spell in between wand shots.
On a side note about that mod, you can boost your actual book spells with an impractical gimmick too (kind of only useful for Meteor). Spell cancels count as casts too. So basically, start the casting animation for any damage spell and then hit O to cancel it. Do this up to ten times and you'll get a +30% - 50% boost to damage (depends on the wand's +%damage if repeated number) when you actually cast that spell for real, as long as it's your next spell.
Also, I didn't realize you actually hated Lightning. I can't stand the element. When the game was first released here, I thought Lightning was pretty cool due to it's air charge attack and how "great" it was for clearing trash, and then I learned how to actually use both Fire and Ice correctly. I also hate it when people just jump around spamming that annoying, screen filling lightning storm crap just to kill 1-2 enemies that would have died much faster to the ground up attack.
The gazer is one of the easiest bosses as a solo wiz/sorc, because it's weak to all elemental damage. When its eye faces you, you can't cast. So you should only attack when it's stuck in an attack animation. Also since it has some impossibly fast attacks (lazer beam, etc), you should never stand left or right or its position. Instead stand above or under it and wait for it to attack. Once it attacks, use evasion to get to its back and cast a spell. During certain attacks the main eye is completely closed, (fire pillars, explosion charge up etc), and you can safely cast away from any position.
Both the Wizard and Sorceress can approach Gazer in similar ways. With the Wizard you can simply use a Lightning rod and Levitate over the top of it. As soon as you reach just over the halfway point, just do Lightning's air charge. It will often stun Gazer. With the Sorceress, all you have to do is Levislide across the top of it, and as soon as you reach the opposite side and turn around, simply launch an air charge attack.
Both of them can also simply walk somewhat close and teleport to the other side to cast either a pillar attack or a spell from a book. The Wizard has the easier time with this approach due to Slow. If you can cast Slow in the middle of the screen and stay around that area, it's really easy since Gazer won't teleport too far away from your position usually.
I'm not particularly sure about spell damage, but I'm about 80% sure your staff/rod's atk power does not affect your spellbook spells.
It most certainly does.
Also, apparently the Amazon got a huge nerf in the upcoming patch. Her Berserk uptime was drastically reduced, and you can no longer simply swing weapons in the air to keep it active once it's already up. You must hit something to keep it going, and its time out timer has been sped up. War Paint's damage was also reduced. The Parry buff is less of an actual buff than just a sidegrade now. It also allows a more defensive style to be played, because you can build Berserk easier, you just can't keep it as long. This should make it a lot easier to deal with trash, but now bosses will be "harder" and won't die in ten seconds or less.