why is castrum and praetorium not an instance

[Pintsized]

Increased HP, damage and healing done is still gonna require the dungeons to be reworked to allow every job to solo it.

Not at all, Turbine only had a very small handful of mechanic changes to any of the LoTRO 'epic story' dungeons, which are in no way simpler mechanic-wise than XIV's, they added an item that you 'use' to apply boosts entirely equivalent to 'Echo'.

Let's face it, that's EXACTLY what XIV does in the forced-solo instances after you fail them once, SE recognised they had to do that back in beta (or was it even further back in V1, I don't recall now) otherwise many players would never get beyond level 5 in their class progression!