Should DA:D bring back Companion specific Specializations?

Yes, BUT - they shouldn't put core necessary abilities where only one character can get them. No merrill/anders situation where only one of them can heal. Merrill didn't just not have a healing spec she lost access to the base class spell tree Creation and it's healing, which made playing with her as your mage when Hawke wasn't one harder then it had to be. DAI handled this better in that, while only Vivienne gets a heal in her spec, the Barrier system that replaces most healing in that game is available to all mage companions.

So, yeah, if they keep it so that every companion can fill all their classes basic roles in the base class trees (eg. all warriors have access to taunting and Guard, if thats still a thing, regardless of their spec) then having more unique tailored to them specialisations would be great.

I went with yes we are all different who wants a cookie cutter character companion? I always built my party around their strengths and weaknesses.

This was my main gripe about it, together with others I have mentioned above.

I felt that was the problem with Inquisition if I needed that particular ability set and was not of that class so I could take it myself. As it was, I hardly ever used Vivienne when I was a mage, as Knight Enchanter rocked, but tended to include her for the same reason when I was some other class. To be honest, if that wasn't the case, I would hardly have used her at all.   Ditto Sera when I was an archer.

I never really felt that way with DA2, my decision over who to include in my party mostly depending on which grouping would be easier on my ears once I established which ones were most inclined to bicker or snark. I also tended to role play more with DA2, so, for example, would use Averline more within the city provided it didn't seem to compromise her position as the official law enforcement, whilst sticking to Fenris more outside of it or where it seemed a bit more suspect.

I agree that it would have made more sense for the companion to be the trainer in DAI, which would actually have replicated the system with DAO for some specialisms (although all could ultimately be learned from a book), but since I would rather not have the PC duplicating the specialism of the companion when there is only one specialism (unlike DAO), I would prefer they did something completely different for DA:D. Alternatively, instead of the trainer coming to our base, perhaps have the companion or advisor recommending visiting a particular NPC, shrine or other location where you can be trained/do research into the specialism and may be set a specific quest that allows you to graduate. Definitely not being sent to several different locations to collect random resource drops, though. Something that actually tests you skill that is relevant to the class and specialism.

Unfortunately, they have been progressively restricting our scope in this respect. For example, back in DAO with mages we had a far more extensive selection of basic spells plus 4 different specialisms to choose from. Rogues were able to dual wield something other than daggers and Fighters could dual wield and could also use a ranged weapon if you allocated points to allow for this. We also had two weapon slots, so you could interchange between ranged and melee weapons mid battle. This meant there were considerable possibilities for individual customization, allowing you to give out attributes as you saw fit but at the same time avoid duplication.

DA2 reduced the possibilities for customization but given their short development time it was understandable. I didn't have a problem with companions having unique specialism, which meant you had to use them if you wanted to access those particular abilities, and there was enough variation in what was available in basic abilities that you could ensure your favourite companion had the sort of skills you needed from them.

The problem I had with DAI is that they reduced the number of basic attributes you could select from still further whilst not giving the companions their own unique specialisms. Whilst it was still theoretically possible to customize the basic skills of a companion to be the same as those of a less liked alternative, each had only one possibility for a specialism, which could mean duplication with the PC. As I've already said in my earlier post, this did allow you to select the specialism of a disliked companion if you were from the same class, I didn't appreciate the reduction in scope for individuality of both the companions and the PC. I would like to see this reversed in DA:D, so at least the PC has more than one specialism available to them and a greater range of basic attributes, but I'm not holding out much hope on this. A lot depends on what the "leaked" skill tree layout implies and whether we are even allowed to control the development of our companions.