I'd have to argue that pure int mages are already pretty viable. In a situation where there's 4 birds or bears and 1 pure int mage, that pure int mage, if you know how to play if effectively will do more damage than the rest of the team combined.
Mastering survivability is the challenge - knowing when to use mana shield. Btw, your mana regen is so fast that even if your mana shield is depleted, you can still cast spells like normal!
For me though, the challenge is mastering this build in pvp. The majority of my deaths come from surprise attacks from enemy birds.
Edit:
The pure int is a hard to play build and it should only be played by veterans who are comfortable with having tested out several builds. In particular, try the transition from pally to hybrid. If that goes well, consider pure int. If not, stay with pally or even strength mage. Dex mage is only if you liked the transition and want to try something different.
Damage potential is huge, but so is sudden death. It really depends on your play style.