well a way to quick fix the current thing without destroing the simplicity keep modern and resemble classic is some talent changes aka skills like this .
add flamestrike to generic spell not talent independant . (with like 120% spell power )
add meteor to flamestrike location and deep impact to fuel the fire location . take fuel the fire to deep impact location.
add a new flamestrike only talent which will also change to flamestrike to cast to target or cast to cursor choice and add it to the current meteor location. now both the new flamestrike and fuel the fire talents is behind path of flame which is flamestrike talent to begin with while meteor had nothing to do with it .
an idea would be the that the cursor flamestrike has more damage boost ( as it is ) while to target flamestrike applies slow like it was back in classic. so like cursor flamestrike increase damage by 40% and flame path damage by 20%
while to target flamestrike increass damage by 10% and applies 30% slow .
add phoenix flames talent back but to single charge no way to be increased with 15-20 seconds cooldown, get boosted by feel the burn and from the ashes the same way the fire blast get boosted by those two. also by blast zone the same way meteor and flamestrike get boosted.
phoenix flames should be added at surging blaze talent location and surging blaze removed entirely. maybe add a unique new phoenix flames interaction with ignite like after the explosion phoenix remain there for 1 second and everyone within range takes damage by ignite 600% faster . so after 1 second 7 seconds from ignite would pass which would make easier both take care of ignite as burst and remove ignite if you wanna take advantage of polymorph and maybe master shepyard without your ignite break opponent polymorph .
swap location of scalp and frenetic speed .
make frenetic speed like this : when fireball triggers scorch or firestarter you gain 30% increased movement speed for 3 seconds and your fireballs become castable while moving for the same duration .
nerf scald to 35-40% increased damage .
EDIT EXTRA SOLUTION :
second idea about keep some of our mobility without need of scorch return or multiple phoenix flame charges.
frentic speed and scald remain as it is at talent tree location .
frentic speed remain as already is or can also be triggered with scorch or firestarter
scald rework : your fireball deal 10% increased critical damage and dealing critical with fireball will make your next fireball during the next 6 seconds castable while moving .
) . if it was in the generic talent tree or at least at fire it would be cool idea to test it play it but how good and balanced is different story .