I like what I've seen so far for 1.4.
I currently have 3 alts at Level 12 so found it interesting that Level 12 was the base line for how they want Time to Kill (TTK) and Time to Be Killed (TTBK) to work - ie how tough the NPCs really are.
With a relatively optimised Level 12 (all blue weapons and gear, with some thought into the build with regards to stats) I had no issue soloing against Level 15 normal and veteran enemies. I haven't tried it yet on Elites but I expect I could take them on.
If they get the linear damage model correct, the difference between 12 and 15 should be the same between 30 and 33. World Tier 4 should be solo'able by CasualCore (I think that is the term for greater than 500 hours but not hardcore) if the TTK at 12/15 is anything to go by. So I'm really excited for that.
Cheers,
It will be linear

If you haven't done so, watch the most recent sotg, they show level 33 npcs in their test environment with the new ttk and ttbk.
Even for the standard, if it wasn't a Horizons game maybe.
I won't pay £50 for a digital game now - BF4 was the exception I think. Like hell am I ever paying £80 for a pre-order from the Windows Store for anything.
On topic 1.4 stuff - yay. Need a decent shooter/loot game again. Hope the fix the crap drops etc.
The drops will be fixed, more evenly weighted, and increased pending world tier and difficulty setting on incursions.
Will be awesome, especially in the pve world.
I still think that if you are min maxxed now, we will still be min maxxed post 1.4 but at least the pts will give us time to see what we need to do to gear to get min maxxed and iptimised again in prep.
I just want to jump right into tier 4 lol