Unfortunately, blood biography combined with magical checkins and a spell-based binary search (probably using spirit planchets and generations of "retired" agents as spirits) to locate bodies spells doom rather cheaply as government spending goes.
Blood bio, cast with a drop of a ctreature's blood, gives answers to:
Who are you? (The name by which the creature is most commonly known)
What are you? (Gender, race, profession/role)
How was your blood shed? (Brief outline of the events that caused its wound, to the best of the victim's knowledge)
When was your blood shed?
Finding the corpse will have blood in its wounds, which then provides a "brief outline of events." It is reasonable to assume that a brief outline will discuss the method of attackers. Which then, (papers please!) will link them to the last internal checkpoint by their class descriptions or other characteristics linked to their identities.
To be clear though, the public side of things will be absolute silence. Because the public doesn't know about this appearance of weakness, there will be no advertising the weakness. (Otherwise people get the idea that harming the secret police is possible, and we just don't want that...) Reprisals are fine and all, but an aura of omnipotence is better. If the team missed any of its checkins or procedures, their supervisor (to the function of his ability to have fall-guys) will be tortured to encourage the others. If there are some rumors, some of the "usual suspects" will be rounded up and executed for a trumped up charge.
In terms of team notification, every team will, being lawful, likely follow "modernish" police practice of "check in with home base." The logistics of this vary, depending on infrastructure.
- Visible tech: A napoleonic semaphore is not out of the question, especially with items of "whispering wind." (Given how cheap this makes individual messages, combined with the efficiency gains from modern communications and the ability to spy on the communications of a populace, I see no reason why a lawful evil society wouldn't have one of these networks.)
- A wizard did it: Telepathic Bond may be made permanent. Every squad of agents should be placed in telepathic bond with their controller "back at base". Given the communications capabilities that this implies, it's the cheapest possible communications network. An "empire" (evil or not) lives and falls on its communications, which means that there should be a correspondingly high priority assigned to this. We can assert, however, that the idea of battle-ready flying squads ready to teleport to help requests may not be part of the repertoire, likely due to infighting and other politics. Still, even presuming that these aren't "always on" (maybe the controller is managing multiple squads) squads should check in when before they expect trouble and after they're clear.
The players get one missed checkin as a grace period, Then a "ministry of divination" (I'm assuming nation-state resources) steps in with a series of spirit planchettes and does a binary search to find the last location of the missing team (as a function of the region that they checked in from). The binary search only needs to be of a region the size that locate object (remember, both a corpse, the corpse's robes, and the identity documents marked with a specific arcane mark are all items) can cover. Happily, the players removed some of the evidence there, but a corpse is still an object.
That binary search takes exactly as long as you wish, as it's a function of the resources invested into the "ministry of divination"'s binary search capabilities and whether or not the "spirits in the area" are favourable to which side. Of course, if I was an lawful evil ministry of divination, I'd make sure that the spirits in the area were particularly well disposed to me: any spiirt that provides a useful answer has their family rewarded with a lowering of quota or other "random" bureaucratic positive outcome. Any spirit that obstructs this will a) have their family harmed, and b) be otherwise removed using normal mid-level adventurer capabilities.
If I was doing this in 3.5, I'd make sure that the communications infrasturcture all had the necrotic cysts implanted in them so that the parent-cyst could scry (and remote take over) any of her agents whenever she desired.
The d20srd FAQ appears to answer this for us, rather helpfully, in a question about future content:
This site currently contains content from all sourcebooks published by Wizards of the Coast that contain open content. This includes open content from the following books published in the official d20 SRD:
- Player's Handbook
- Dungeon Master's Guide
- Monster Manual
- Epic Level Handbook
- Deities and Demigods
- Expanded Psionics Handbook
In addition, the following open game content has also been included:
- Razor Boar and Scorpionfolk from Monster Manual II
- "Variant Rules" from Unearthed Arcana
However, not all content of these books are covered in the SRD, and sites like D20SRD are not permitted to publish it. For example, some monsters are considered product identity and omitted.
Best Answer
Let's see. Iron Heroes is definitely good. The Conan d20 RPG from Mongoose tends to favor warrior types, it lets you play a ritual caster if you are really into that but most of its assumptions are "stick a sword through it."
For 3.5e the Tome of Battle: Book of Nine Swords had a lot of high energy martial arts stuff in it. We've used that in some APs.
I see this WotC article on ideas for de-magicing D&D posted in a bunch of places.