I have a Wiz19 and a Sor18. Neither one are nukers.
The Wizard does not have any enhancements for damage. But has Empower and Maximise spell feats. Wizards get a lot of spell feats. And I thik they are good feats to take at some point.
The Sorc is totally CC based, and does not have Empower or Maximise. Yet has spent a lot of AP on Fire/Ice damage enhancements....mostly because there was nothing else to spend them on.
On the Sorc, I did not want to take Firewall. Yet it is just too good a spell to pass up.
Both chars prefer to not use it. It draws too much agro.
CC spells are my prefered spells to cast. A controlled crowd cannot hurt me.
But rednamed bosses leave you litle choice but to burn them down.
Firewall is by far the most efficient spell to use to damage things.
Both my chars, despite not being specced for nuking, can still throw down a mean firewall when needed. And can still do so many other things as well.
It is just too good a spell to pass up.
IMO, you need to carry it. Even if you do not plan to use it.
Evaluate each situation. And when it makes sense to do so, throw it down.
I don't typically use it for trash mobs. But for end fights I quite often fill a room with fire. Not because I want to. But because it is the best thing I can do at the time.
Sometimes you can't play your char the way you want to.
Sometimes you get preasuured by other players to play your char a certain way.
Sometimes the dungeon/monsters make one tactic superior and others inferior or useless.
So come prepared to adapt.
Play the way you want most of the time. But be prepared to play another way at times too.
Either when needed, asked, or when it just makes sense to do so.