Should the DLC ever effect the main game?

If it have a huge impact on the story, Nope
(Traspasser, the Arrival, Leviathan...)

Fuuuuuuuuuuuuuuuuck no. I don't want to see a season pass in a Mass Effect or BioWare game. That right there instantly kills my interest in your game. I don't mind what they've done thus far (except blOmega) as far as things that ADD to the game but please don't overdo the dlc dependance or cut content (like blOmega).

It's kind of a catch-22 though, isn't it? If DLC affects the main game, then it should have been in the game to begin with (Javik/Leviathan). If it has no effect, then what is the point of it and why can't we get something that actually matters instead (Omega/Citadel)?

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DLCs can only add to the player experience but cannot influence the game choices already made without it.

I can't see it in any other way.

I think it should, but i feel it shouldn't affect the story to the point to where it causes plot holes for the person that doesn't have the DLC.

Dlc that effects the story can be a problem in a way, if we think of Awakening & Trespasser for Dragon Age & Arrival for Mass Effect, these events are actually the true endings of the games, leaving the player that hasn't played them wondering just what's going on & something that adds to the story can also be considered cut content.
I'd like something fresh & new something that can effect the branching narrative of the series if played, but will also have no impact if not played, as an example I'd use Jaws of Hakkon for Inquisition, as all it really adds is lore for the Avvar barbarians, but is a fun experience for the player too.

Just my thoughts.

*affect

I'm not sure my thoughts on it make a lot of sense, but what the heck, I'll give it a whirl.

For me, Trespasser in DAI and Arrival in ME2 were kind of important and really expanded/extended/completed the story ... an argument for them needing to be in the original game ... or perhaps a free extension (ala EC).

Descent seemed incomplete to me and totally disconnected from the main game ... so while I loved the visuals, it felt kind of empty.

It is hard to think of ME3 without Javik.

So where is this all going? If you are going to drop a DLC on us ... it should integrate into the main game (references added, scenes changed, outcomes modified to the main game) so that it becomes part of the bigger game ... to include new characters. The game should be a standalone without the DLC. So something like Trespasser should be a no-no, unless it is free. Same for Arrival. They complete the game and should have been part of the original release ... or a free release later.

There can be exceptions ... like Pinnacle Station ... which are just fun excursions that don't effect the story (other than give you the opportunity to max your game manifest with all the really cool gear) ... but they should just be for fun and you would be totally fine playing the game without them.

Leviathan should have been better integrated into the main game ... but other than lore (and some toys) it was fine if you never got that DLC. So ... I guess I'm saying I want it both ways ... integrate the DLC with plot/lore implications better into the main game ... but allow the main game to stand alone if you don't get the DLC.

Another point. For shooters, I think it is easier to throw in DLC or expansion pack ... more maps, more missions ... the story is rather thin. But for RPGs, because the story is (supposedly) the thing, DLCs become trickier. Corporate pressure (gotta pay attention to the bottom line) makes it tough to fully integrate DLC into the main game, but the story after the story or a disconnected story within the main game can seem like a rip-off.

I liked how From the Ashes integrated into the main game ... hard to imagine the game without it ... and yet the game is fine without it. Leviathan was OK, but once complete ... memory-holed as if it never existed. It was a missed opportunity ... but would/could have changed a lot of the main game.

I vote for DLCs that add more to the lore. They should delve into the backgrounds of the characters, to flesh out their personal histories and the events that shaped their attitudes and perspectives.

For example - a Prequel DLC for Shepard that allows us to experience the events on Torfan, Akuse, and Elysium, all the events that led to our hero's psychological profile in ME-1. Wouldn't that be fun? It's not critical to the ending story, but it would be so cool to explore the 6 different outcomes (3 events X 2, for P and R outcomes) - and all of them included in 1 DLC! Now that would be, I think, a big money-maker for BW/EA and a HUGE boost to our enjoyment in the franchise. A DLC that we can re-play and re-play to our heart's content. It wouldn't need to have a save transfer file; a stand-alone DLC would be fine.

Right, but who would play them as a prequel, especially after the game has already come out?

I like dlc to give me a deeper understanding of the story but not affect the outcome.

What they did with ME3 I liked; they had a lore dlc (Leviathan), an action dlc (Omega), and a fun, silly dlc with our companions(Citadel). All of those added a lot to the game but had no huge effect.