I'm level 10 and had Tristian cast True seeing on my Eldritch Archer so I could hopefully get around the blur (concealment 20%, so 1/5 hits guaranteed to miss) and displacement (concealment 50% so 1/2 of all hits miss) of some of the creatures of the otherworld, but it doesn't seem to work.

As an example I need to take down a poisonous primal manticore which seems to have a blur type of concealment (20% miss chance). I actually once managed to inspect the creature character sheet so it showed the "blur" buff on the creature with an infinite duration.

In any case True Seeing doesn't mitigate the concealment of 20%. I tested Tristian's Level 1 cleric spell "Faerie Fire" which, when casted on the manticore does successfully bypass the blur effect. I also found that I could use the level 3 Magus/Wizard spell "Dispell" to remove the blur effect, so that works as well.

Since the "True Seeing" spell description gives a special mention in it's description to countering blur and displacement effects, I'm guessing this spell is bugged.

I have spent a bit of time on d20pfsrd.com (fantastic resource BTW) to better understand the mechanics, and tried looking online at other peoples takes on how true seeing should work in the game (some comments were suggesting some creatures with innate concealment can't be seen with True Seeing, but I can dispell the blur effect from the manticore so it doesn't seem like an innate ability).

True Seeing is not working properly for very long long time.

It's not countering blur and displacement effects as it should, so Echolocation is better than True Seeing by most ways.

The best value of True Seeing is it can countering mirror image, even Echolocation can't do that.

For the rest, it just like See Invisibility, +20 Bonus to Perception when detecting stealth enemies.
(Although they're not always work during my last test, and I don't know what type of bonus it is)
And they can countering total concealment effect like Natural Invisibility and Greater Invisibility, at least from what I heard.

I didn't know that it countered mirror image, so I thought I would give it a test by casting True Seeing on the manticore :D

Basically ran poor Tristan in there to grant one of the manticore's True Seeing, then cast mirror image on my arcane archer and bought him down to take damage from both.

True Image does indeed work with mirror image; the manticore with True Seeing would ignore the mirror images and do direct damage to my archer, while the one without would more often then not destory a mirror image instead.

From a bit more testing I think I understand the differences between Displacement and Greater Invisibility better:

Level 3 Spell Displacement:
50% Concealment

Level 4 Spell Greater Invisibility:
50% Concealment
+20 to Stealth check
+2 Circumstance to attack bonus when attacking
All opponents are flat footed when attacked by the person under the effects of Greater Invisibility

I don't think I understand stealth, since the Perception DC from the manticores seems to change even if I'm standing still. For example my stealth total is 41 while standing still (and under the effects of greater invisibility), but I still lose to perception checks much lower than that (27 for example), although sometimes it is higher (36 in another case); in fact it looks like the DC is whatever the manticore rolls in addition to it's bonus as a perception check.

So I'm not sure if True seeing wipes out the +20 Stealth bonus given by Greater invisibility, since I don't know how to test it properly, but for the most part True Seeing downgrades greater invisibility to normal Displacement.

Unfortunately as an Eldritch Archer it seems tricky to counter displacement or blur, at least magically (I see an Improved Precise strike, but my dex is only 16 and I need 19 and an attack bonus of 11 for that feat).

Access to True Seeing is a while off and isn't going to help anyway, though level 19 will allow me to grab a limited number of wizard spells including Echolocation.

In my current game I don't have Octavia in my party, but she does have Echolocation; the problem being is that doesn't help my Eldritch Archer since it's only a personal buff, unlike True Seeing which can be given to others.

Best solution would be to fix True Seeing to deal with the Blur and Displacement effects it claims to deal with, otherwise Tristian's Faerie Fire seems to be the only spell counter I know of for blur and displacement that benefits the group.

On another note, I didn't see any +20 bonus to Perception while under the effects of True Seeing (I gave one of the manticores greater invisibility), unlike invisibility itself which shows an immediate +20 bonus to stealth. I could target the Manticore no problem, but perhaps given time a failed hidden perception check on my part might make him untargetable for a round later on.

EDIT: It may be that True Seeing is giving a +20 bonus to Perception or negating the bonus to stealth given by invisibility, since I just rolled to discover a Doom Spider that looks to have Greater Invisibility on itself. My base Perception check is +14 yet the log detail showed the modifiers total to be +34 (14 + 20). The same Doom spider has the +50% Concealment as well as the circumstance +2 [concealment] bonus to attack and flat footed bonus when attacking other party members.

EDIT2: I just got Improved Precise shot on Ekundayo and it isn't all that impressive since with 50% concealment (aka "Total Concealment" I think), it has no advantage, so that seems a waste (well it should still be good for blur's 20% concealment, and since I know it doesn't work against 50% concealment I don't need to worry about dumping all my points into dexterity to get it and can focus on just maxing intelligence). Blind Fight definitely looks to be a better counter, but only applies to melee as far as I know.

During the second part of the Tenebrium ruins I ran into a solitary wild hunt archer (apparently before the patch this room was infamous for being incredibly difficult as it had quite a few more of these guys you had to contend with) and their shots against my Arcane Archer with Greater Invisibility didn't need to deal with the 50% concealment penalty (as in I might as well of not casted it) so I thought that maybe it had to do with them having "Improved Precise Shot", but with Ekundayo he can't bypass 50% concealment so it must be some other ability they have.