Oh no doubt it is viable, but is it the best choice if playing Skarner top?

I tend to disagree. Seismic Bastion gives a shield as well as a movement speed buff lasting 6 seconds and Ghost gives you a 27% lasting 10 seconds. Indeed you do travel more ground using Ghost BUT you have a cooldown of 210 seconds compared to a cooldown of 16 seconds. You already have a stronger version of Ghost, it just doesn't last as long.

Flash on the other hand completes the set of Movement based buffs for Skarner by providing a blink ability that will instantly travel you 400 units. Combined with Seismic Bastion you should be able to pursue and Impale any target or avoid being killed if fleeing.

As for Heal, it does provide a nice sustain considering you no longer have one in lane when going top. The downside is that once it is used you have a long cooldown until it is ready. Heal however is going to be a waste if the enemy isn't blowing up your shield. Some thing with a little more killing power or suppressing power like Ignite or Exhaust is going to assist you more. Ignite especially against top lane champs as many of them have inbuilt sustains.

You no longer do.

To reiterate it Is viable, but in normal and ranked games, other spells are going to be a wiser choice.