Combat should NOT be a jack-of-all-trades.

I still think that it should be optional, and what's wring with making your own decisions to have a companion or going alone? And they should set up a balance to have players decide what they want without penalizing players.

There seems to be a bit of confusion about combat that really needs to be cleared up. Dragon Age Origins like Baldur's Gate before it emphasised strategic combat, not tactical combat. Tactical combat is a short sequence of moves, strategic combat represents long term planning involving positioning and mobility. This emphasis on positional play is why BG and Origins had a top down camera.

When people say Dragon Age 2 keeps the tactical combat of the series, these people continue the incorrect idea that Dragon Age Origins was about tactical combat. It's not, it's about strategic combat. Something impossible in DA:2 for no other reason than the absurd wave combat.

People may like the action oriented combat in DA:2, but to say it kept or improved the essence of the DA:O combat is wrong.

Honestly, depending on who I use in my party, I often get a ton of combos with my companions without even trying.   When I first played on 360, when the game slows down a second because you're scoring a combo, I kept thinking, "Hell, I'm overloading the 360 with all these graphic effects!"

This is usually a scope problem but I completely agree that it feels better when your teammates feel like their own unique character rather than a mirror image as you said 

Yeah, see, I loved that in DA2, with Mages AND Archer Rogues. Point blank, albeit the damage probably was less than the bow attacks, you pull out a knife and went Legolas style. That was a beautiful bit of realism!

This is what the team should invest on their combat design entirely based on motion capture. I think this will be a very good investment to hire experts of swordfighting, and acrobatics (for dodging and jumping) to make combat more fun to play.

DAO combat was terrible. Spongy. Stupid lemming AI. No consequences ignoring zones of control, just mindless hack and slash and pile the conga lone on the mages.
It was so bad I played only until end of prologue in 2nd playthrough.

DAI evolved to Action driven gameplay. Many hate it but it is a consequential evolution and it works a lot better than the mess in DAO.
The last system with working isometric pausable RTS combat was Baldur's Gate I believe.

With mods, Elder Scrolls can have very good combat.

Personally I enjoy fully controlling a party of characters in combat. What abilities they use and when, who they attack, whether they move or hold. It has a joy you don't get from just controlling one guy.

I enjoy having a pause button which allows me to easily control those characters. And pausing gives me all the time in the world to decide what to do next, to assess my enemies, the terrain, my own abilities and best positioning - and decide what the best strategy/tactics are. This is fun for me. I can, and enjoy, pausing after each set of instructions are completed to give out more, maximising my use of time and letting me watch the cool animations instead of being too distracted by what I'm doing to notice them. It also let's me continue to play when I'm having a bad time with my chronic illness.

I like the Tactical camera, it makes surveying the battlefield and placing AOEs much easier.

I prefer having whether I hit, block or Dodge being determined by character skill and not player skill. As when I play games that use player reaction times, fighting is mostly just button mashing for me, I don't have time to strategize or think much about what I'm doing and it's not fun (i realise there are people who can actively dodge, attack, and block while still thinking about tactics and what to do next but I'm not one of those people, my concentration and reaction times are not that good). Besides it's annoying when I make a character who's meant to be (and is built for) being a dextrous, acrobatic rogue but they can't dodge for shit because I can't, kills the rp fantasy.

The tactics menu isn't strictly necessary if I have all the above, but I did enjoy using it for the easy fights that didn't recquire as much thought. To zoom in on my character knowing the rest of the party would do what i wanted. Being able to choose combat behaviour for each party member (Whether they're aggressive, defense, or passive. Whether they favour melee or ranged, etc) is great. Being able to say 'use this ability any time you see an enemy' but 'only use this ability when you see a powerful enemy (elite, boss etc)' and 'use this ability when this many people are clustered together' were great. The use, don't use, favoured options in dai could result in the party using abilities in situations i wouldn't want them to, archers kept running into melee and no one obeyed the hold command. So in dai I mostly didn't use the ai and stayed in tactical camera in fights (also because the active character wouldn't Auto attack in 3rd person).
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Bringing it back to the OP, and whether combat should be Jack-of-all-Trades or not, I'm not sure.

Naturally I'd like it better if they leaned into the Strategical Party Play with Pause, focusing on making that better and innovating new ideas in that area. But if I had to choose between action twitch combat and the hybrid thing that dai had going on I'd vastly prefer the hybrid thing. I didn't like the way MEA took away the pause button and squad power control, for me it's the least enjoyable combat in the mass effect series because of this.

It occurs to me given the nature of Role Playing...why not?

Now this is with the proviso that of course in DA mages tend to have a little more uniqueness in the universe coupled with how mages are traditionally included it will be hard to include them in this. But the base idea of a jack of all trades is a legitimate idea for any type of warrior that you might want to be. As long as one keeps in mind the second part of that sentence...master of none. So yes a character should be able to invest in a wide variety of skills and attributes but with the understanding that will be a sacrifice somewhere else in the line.

Which was Andromeda's problems. While Andromeda's classless system was pretty good the issue is they didn't have any other limits on it to balance out so you could literally pretty much become a master of all. A level cap I think off the top of my head is the best way to go.

‘Useless’ is a little bit harsh, in my opinion, at least.  But it does need massive improvement if they’re going have it again.  It required way too much effort to be effective (and I used it almost exclusively).