Fire + Sun or Moon, those would be the best ones for PvE, 100% Preferred? Chaos + Water, Chaos is so fun (would be even more if the was a second damage spell that worked on mobs) and water only lacks a real AoE, and the combo would be my only combo ever needed.
Nothing stops the fire mage with anything else...Sun is good as support but not necessary since Fire + "TURD" magic skill tree is still king.
I love Death/Sun but this restricts you to all things living. Some other good combos: Water/Life with heal mods Sun/Life Fire/Sun Fire/Life
I was Fire/Life for a LONG time and really loved it, a couple things I struggled with a lot (ie: things that were highly fire resistant: dragons/lich bosses to name a couple examples). Then a couple months ago I switched to Fire/Taming and am really loving it. The pet can't compete with the DPS of a lot of other options but having a pet run interference/hold some aggro off me has turned out to be more useful than straight DPS for me. I generally prefer to play solo because waiting for groups to form/fill and get started drives me bananas. When I log in with 'x' minutes available to play, wasting 30 minutes getting a group ready is a huge Nope from me.
I'm Air/Sun. I'm mostly a PURE Air Mage with just Sun support for the crits from the INT buff. I'm 120 in ALL air skills including the mastery and with my gear I'm over 300 air attunement. It isnt the most damaging school, but you get 2 AE's that stun along with lightning bolt that also stuns. I absolutely love it. Pair it with a Death/Earth/Fire mage for any of their AEs and its lethal. It's not really a solo school but all groups love to have at least 1 air mage and I plan to take it even further to see if i can increase the overall damage ceiling. I'm having alot of fun with it...and plan to keep it. Plus it fits perfectly into my character name and my heraldry. Play what u enjoy. You dont have to be the meta to enjoy our game. With enough xp you can make anything really good.