Here's what I think - it's all ok with all the events happening the very same year. Yes, those events do have an intended order of accomplishment, but referencing to Zurin Arctus, each Event is preceded by Prophecy - but without the Hero, there is no Event. The ESO events are preceded by Prophecy, and regarding the Heroes - well, some of us come to participate in an Event, while the other don't. Combine it all with the idea on the nature of the Elder Scrolls I posted some time ago and you'll see that everything fits quite well in just one year of 2E 582. Yes, doing, say, the Summerset Chapter before the Morrowind DLC is said to change Veya's character to Earl Tundilwen while Veya's fate would be ultimately decided in Vvardenfell. Another example is the case of Sarvith Yunlin and Saravith Yunlin. Well, I'll speak of it a bit later, but even if the devs would not have implemented that thing with Veya, everything would nevertheless be ok.

The devs do change dialogues for those cases when we meet some particular characters for the first time, but that has nothing common with making different DLCs chronological and all them happening in the very same year or several years - remember, we all are reading the very same Elder Scroll depicting the same events of that Second Era year, but just as it happens IRL, we read it differently and understand it differently. Some people read the Scroll from the end, the other start from the very beginning, while the rest only read those parts they want or need. But all the events are already inside that very year. It's just the matter of chapter order and this is why they make that name and dialogue changes - to make those reading the scroll from the "end" think they read it from the "beginning".

Sorry for a long part above, but I thought it necessary to try explain it before quoting the lore on it's time concept. I can't recall how those 10 years rolled in Arena, too many years passed, but in later games the years rolled in real in-game time. The years rolled, but the world stood still, though the devs did really a great job to make us believe the opposite. If the world did not change, then that linear time was just an illusion - this is why the lore recognizes all the events started in 3E 427 as the events of that specific year and the same way it treats the events of the ESO.

In ESO we have several accounts of what I tried to explain above:
- Raynor Vanos - "Don't think of time and space as a road upon which you travel, but rather a rope, or a cable. Many threads, all bound together with no beginning or end".
- Teldenrinde's Murky Time - "[The calendar] is like a bowl of water. The day and the night swim in the bowl".
- Sotha Sil - "actions, both good and evil, are inevitable. Locked in time. Determined by chains of action and consequence". "Every action we take can tip the balance of the flow of time", he says.
- The Augur of the Obscure called time a "chronosymphonic disc" and spoke exactly of the thing you do - "Linear time is so overrated. Just imagine, you could die before you were even born! Wait ... that's horrifying isn't it? I'm sorry. Never mind".

Well, honestly, the Augur's words only sound that horrifying - we all actually had been dead for an unspecified amount of time before we were born, but I don't recall anybody horrified that much of that fact . Change the words "time and space" and "[The Calendar]" I mentioned above to "ESO", and the word "threads" to "quests" or "DLCs".. whatever.. and then read it again. That would be much more comprehensive. This is what I mean, no linear time on Nirn - it's just an illusion, though suprisingly it also effects us, the ones called in the lore the Prisoners and Heroes, the players, those who should have known it's nature by default .

The Psijics teach us those three incantations - Undo allows us to step backwards in time, resetting ourselves and our position to what we were seconds prior spellcasting, Time Stop and Accelerate are seemingly almost the same Alteration spells in their essence differing only in the object of spellcast either on self or on target (ground). In order to change something globally you'll have only two options - either to summon Numidium or to "Dragon Break Dance" on the top of a tower, but even in that case you won't be able to change anything - your choice of eating either a chocolate or a strawberry ice-cream would end with both options having the same consequences. Well, there is the third option with that Nchuthnkarst Dwemeri machine, but it needs further development in order to be researchable. The world of Aedra is static, for stasis they are. For now it is "no beginning or end - it's like a bowl of water, or a cable with many threads bound together".