Just keeping with OP's PoV I created character last night taking Ignite, Contamination, and Peace of Mind. On current build on Classic difficulty I've solo'd the ship fights, beach voids, Burro/Kana, Turtles, Silence, Crocs (used Electric Discharge Scroll), Card Players, Frogs, Silent Monks, pulled a patrolling Ranger (dinged Lvl 4). Just finished "The One" and am cleaning up the magisters now.
At lvl 1 most things died to Dragon Breath, Cont/Ign, wand down.
At lvl 2 Purchased Haste, same strategy. The wand that drops from Turtles works well with build
At lvl 3 I now have searing daggers and poison arrow. Delaying turn to go 2x in a row works well, blow up their MA with the targeted spells, ignite/contaminate puts the dots on them, generally a turn or 2 of wanding finishes job.
At lvl 4 I now have enough spells that it feels much more like a traditional Geo/Pyro build. Same strategies but I now have much more firepower and Ignite/Contaminate are relied on less heavily.
The point? Nothing really, just that these spells are viable and I personally had fun testing this build out. They are still not even close to my favorite spells but when they shine they can shine brightly. Their were several fights that were over in a couple rnds with all enemies burning/poisoned and me just regaining HP/Shields while they died

Rules for this run was no Companions, No fleeing fight, No abusing stealth, No buying scrolls/pots and I also try to avoid using scrolls as well. I used Turtle Wand and the best shield I could find so far. Migo's Ring and Teleportation gloves are also being used as soon as I can obtain them.