Back in DomI this was one of my favourite spells wen playing Jotunheim.
Now it gives more effects for more gems & less mage time, so no reason why it would still not be good.
What many people might miss is that 50% of those soulless for Jotun will be the extremely strong soulless giants (strenght 24 IIRC). These guys breach fort walls like butter!
A favourite tactic of mine at the time was to round up 50 or so of them, hand them to a Norna with guards orders & a small jotun spears + winter wolves army (basically, her full leadership values filled), and gate on an unsupecting backyard fort of my current enemy (magically move/walk in additional commanders if needed).
50 Soulless giants will bring down a 200 strong citadel walls in just one turn...next turn you storm in.
Gateway is weaker now offensively, but the souless giants can still be used for this purpose in a more conventional way.