From the technical side this sounds awesome. We would have better server performance, probably resulting in the reintroduction of quality view distance, less lag aso.
But from the overall experience it still gets me concerned...
First i hope this won't result in the already mentioned phasing in the same zone or even multiple instances of the same zone - this would totally ruin the game experience. So i hope this new technique is only applied in the way of "one Node per continent/instance/battleground" as suggested in the Nost. youtube-preview.
With the chat and other social options still intact cross-node, this would lead to better performance without any impact on the game-experience -> plain awesome!
But it would also leave the server open to even higher population peaks without any lag/latency-problems effecting playability and therefore keeping new players at bay. Its partly theory, but it takes no seer to assume, that the already huge popularity of the project leads to an ever-increasing player count if there are no technical issues, that stand in the way.
So lets just assume, that the new system can handle a number of 20 000 players online without technical issues -> 4000 on the Instance/Battleground-Node, 8000 on the Kalimdor-Node, 8000 on the Eastern Kingdoms-Node. With a peak of 8000 players per Node we probably have better viewing distances than now without lags and no npc-loading issues - so an overall really enjoyable experience

.
But we still have extremely overcrowded areas - just imagine the situation in an area like Silithus... of course you can always adjust ore/herb/mob-spawns, but the plain size of the zones won't change, therefore leading to still bizarre situations, that alter the original experience of WoW-Vanilla significantly (areas, where you can't do a thing because of PvP, try questing in the Searing Gorge for example... or taking pvp aside, situations where mob-spawns need to be so fast, that entering caves can be extremely frustrating...).
The technical side is one major concern and this new development sounds really great... but it's only one side of the player-experience, and up to this point the server-policy addressed the whole topic somewhat one-sided with the focus on the technical issues (of course this is easier to address because you can simply improve that, while the other side has "natural limits" you can't overcome - so decisions concerning overcrowding always tend to be stir up some people).
I think a population-cap and therefore a queue-system needs to be thought over - even if you just install it to prevent the Server-population from further skyrocketing (cap at 12000 f.e.?).
I really appreciate the good news from the Nost-Team here - but i also want to give constructive criticism ... and i'm going to ignore the many posts without actual content, that will plainly attack criticism as for being criticism (because nobody of us pays a penny for ... blablabla...)