Do single target illusion spells need LOS, theres mention of area illusions needing LOS but not single target.

Invisibility in paticular, if cast on team members being invis surely counts as loseing LOS.

Subjects can still be seen using astral perception, so casting mage could travel along with invis subjects and keep them in astral LOS?

LOS is required for all casting (with the exception of indirect spells).

LOS is not required for sustaining.

That said, they are still usually visible on the astral, limiting as this option might be. Some good old dispel/counterspelling would be suggested at this point for the reasons following.

But if you spot them on the physical, the visibility modifier for being invisible (-6) would apply to your spellcasting tests that target them. Fun stuff.

Now invisibility is a mana spell, thus it can be cast on the astral plane. My question is if you cast invis onyourself in the astral plane does it make you invisiable, or would the spells signature give you away?

Guess knew the answer but one of two points that have always confused me. Limitless range on sustaining and unlimited number of targets you can protect with counterspelling.

Limitless range is really up to the GM, but I'd say its for the same reason that spirits can use the metaplanar shortcut; distance doesn't always matter with mana. Though you could easily limit the range and then turn the limitless range thing into a metamagic similar in effect to the metaplanar shortcut.

The unlimited targets for counterspelling is a bit different, but not that big a deal really. Though I do believe LOS is required for counterspelling.

Edit: The aura is still there. I've interpreted the man version as a "could the mind" effect mostly and sixth senses like astral sight are much harder to fool. You're actually better off going with stealth alone or a chameleon suit unless you have the improved masking metamagic... and then thats where it gets fun.

Depends. If its mana based I'd say yes. With the physical version I'd say no, but maybe a reduced penalty could apply instead. Even when a non-magician character resists they generally receive the full penalty when its physical to attacks versus that target.