ShiKage's Big Bang Paladin Build

Ground Smash does not replace Power Strike with Fundamentals and Final Attack effectively if you use it correctly. In fact as shown earlier Power Strike is stronger and is more suited for early bosses and PQs. Slash Blast is weaker but again Final Attack does present a possibility of extra damage on more mobs when used correctly and still hits more monsters at once.

Ground Smash does not combine with Final Attack for added damage meaning you'll always get that 300% damage ratio of your range. Even if Final Attack isn't an absolute it's a chance at extra damage per attack. While it may have limited range of effectiveness, you again have to think about it, what if you are in the right place when it activates and hits? That's 380% from Power Strike with Fundamentals + an extra 150% damage at random for more damage. Now add in 250% with an extra 150% possibility from Slash Blast with Fundamentals and Final Attack. That's 400% total damage at chance on up to 6 monsters total.

Now add in this... Final Attack will automatically attack. Even if Ground Smash does strike at weapon speed, it will not get an automatic 2nd attack.

Power Strike has a good probability of getting at best 530% total damage to a single monster.
Slash Blast has a good probability of getting at best 400% damage on up to 6 monsters of total.
Ground Smash has the set damage of 300% on 3 monsters only.

Regardless of range, power, etc. Ground Smash does not stand up if you know how to fight and know how to use your skills effectively and wisely.

Honestly unless you have max speed/jump and use a fast (4) sword with the longest range will the huge range advantage that ground smash has be compensated for. Final attack is a terrible thing to rely on to beat ground smash since the hitbox only comes out once and in the same area you casted PS/SB. So PS/SB gets much weaker when trying to maximize mobility, which is the best way to train when you don't have rush yet.