Agree. And that’s why I wrote this 
…
… and suggested …
And yes, there are some “boom” effects 
and synergy with freezing.
Though I don’t think it’s right to make exclusive combos for a specific group of skills. Sub-class usually grants 3-4 skills, may be more in the future. So if they will be united via some specific synergies, it will / may make filling panel with all those skills obligatory. And that’s an entire panel which means very small space for creativity 
.
But overall principle of comboing skills is totally desirable, at least in my opinion.