He's a really strong 11 point character. He's circle premier armor cracking beast. There isn't anything else that circle has that can crack armor as well as Ghetorix. He's also a smidgen more survivable, although I doubt he'd survive a round of beating from an enemy heavy still, just still I suppose it might help vs a lot of smaller attacks such as from infantry.
Now I play a lot of video games as well, and I do hear generally people in various forums discuss whats better, what can tank more, and what will do more damage. So to get to the point: you don't need to have the best. You only just need something good enough to get the job done. Both the feral and the stalker will get the job done, and both of them have far more utility beyond smashing high armor targets, something I feel ghetorix is seriously lacking. So I don't really see how you should spend the extra point or two on ghetorix when either the stalker or feral is sufficient.
I understand the differences in stats. mat 6 vs 7 on the stalkers, and the 2 extra pow on the axe vs the feral's claws or reach... At the end of the day though, these things are fairly minor differences that won't suddenly disqualify the stalker or feral from doing their jobs.
I can maybe build a case for him replacing a feral in lists that would prefer one over the stalker just in case you run against a lot of rock walls or something, but it's still a trade off for 2 points when there is typically an easier work around.
There is just something flexibility-wise he's missing for me. He's too specialized.