well, if that one combo is broken, then better to replace it entirely with something else, no? Frees up some space when choices are limited. 😉
Still, I do agree with you as far as DA:I is concerned. The skills that are available for each class, tend to be very redundant to a certain degree. So, it either makes sense to just toss in bunch of slots to cram in all of those skills--which is fine--or encourage the player to ignore redundancy? Eh, not sure if the latter is the best design, but it seems to be what is going on here. For two warrior trees, you basically have 2-4 of nearly identical guard generation/sundering skills. Depending on what you want, you pretty much need them to unlock the nice passives or other skills. Clearly, though, it's a waste to eat up 2 skill slots with skills that are so redundant.
The elemental trees for mages are also very underwhelming, I think. 3 actual skills of each type, and most are very redundant: 2 types of walls, 2 types of mines.
Also, all skills, as far as I know (most, anyway), can be reproduced in master crafting, as % activation on hit--which is a very powerful thing, imo--so that can free up another slot.