In short, true sight is far too easy to use on anyone, it is a scroll people of any build can use with a simple investment into lore. It is not uncommon for most people to carry huge stacks of the scroll and even with its limited duration. This has the obvious effect of nullifying a stealth build, no matter how invested in stealth they are. This also has another effect on people who have made dedicated builds for spotting stealth builds to, making their investment mean a lot less, so in most cases it can feel like a waste of feat selection and a build for spotting when joe blogs with no investment at all beside you can just pop a scroll and out perform you entirely.
I am aware stealth needs a counter of course, so my proposal would be the rare few sources of true sight offered from racial abilities remain as is. They are uncommon enough that it doesn't feel too bad to have them remain unchanged, the spell cast from a spellbook I would argue could even remain unchanged as it would require a little more investment slotting multiple of them and using the spell slot to cast it. If cast from a scroll it should provide a bonus to spot instead of true sight fully.
Along side this, I would suggest that a new command -watch be available, anyone could use it similar to -guard but it allows you while close enough to share your spot score with another if it is higher. This would allow a spot build to point out a stealth target they have spotted too at least another a way to simulate guard watch in a role play way and make spot builds a better supporting role than solo option. This could perhaps even scale say 30 hard ranks allows you to share -watch with 1 person, skill focus: spot would allow a second person to share your spot and epic skill focus: maybe adds 2 more for a total of 4 people with decent investment to achieve it.