PC's die. It sucks. It happens. Oh well.
In my last 3 sessions, I've had 3 PC deaths, and 4 other incidents where the PC's HP went well into the negative.
At this point, I wonder what I am doing wrong. Honestly, I'm at a loss. Would love any ideas. Mechanically, the monsters are using simple tactics, CR appropriate, maybe even low-ish. Party is ECL 7-8, two PC's have the Leadership feat. Most encounters in the 7-8 CR range are taxing. CR 5-6 lets them get some confidence, here and there, but feels contrived on my part. Boss battles "nerfed" to 9 from my inclination to go Avg ECL +2-3 for boss battles.
The players are all 25-35, experienced roleplayers, familiar with d20/3.5, very engaged with the game world, excited about game day, and friends with each other. PC's are at varying levels of optimization, although I've encouraged more effective choices, been very permissive with options and re-training, etc.
Example encounter of suck:
[spoiler]PC's learn of secret ritual to someone powerful outsider. Ritual is to occur at night, on new moon, on top of a steep, inhospitable hill covered in thorns and briars, several hours trek through heavy undergrowth from the nearest road, though there may be game trails, etc.
Several days ahead of anticipated ritual they make a trek down road in daylight, stand on cart road, stare up at hill. I described the thick undergrowth as forbiddingly as I could. Gave them accurate distances. They nodded, strategized, and did other things for two days. They turn around and do other things for two days.
The day of the new moon was rainy, bleak, and heavily clouded, and they arrived at the point of stepping off the road. They had no plan to navigate the dense undergrowth, so the trudged miserably for hours through a wet wood, arriving at the foot of a briar covered hill with under an hour before midnight. Already there is a faint green glow from the top. They decide to scout it. The paladin (finally!) summons her flying mount, leaps astride with a loud clank of full plate, onto the gaudily-barded beast, and they wobble into the air.
The hill is about 600' of horizontal distance to the top, but steeply sloped, and covered in thicker, thornier briars than what they have traversed thus far. The players awaiting news at the bottom begin an intense trigonometric discussion of optimal flight angles up the hill. They clearly understand the set-up.
Meanwhile, they shiny, loud, obvious full-plate-covered paladin, flies up the hill, and sees at the peak a flat, cleared area. Drawn on the ground is a complex seven-pointed star diagram, which glows an eerie green. Seven robed figures are chanting. A few glance up at the paladin, but the chanting intensifies, as does the green, pulsing glow beneath them. The paladin strafes a few times. The wind becomes intense. Chanting rises. The paladin is unable to guess from her observations which cultist might be the leader. So.... she guesses. 1 in 7 chance. She shoots a few times from moving griffon-back, with an unenchanted short bow into heavy winds. Rolls utter suck. Flies down hill, shouts over wind to companions, and returns to the calling ritual. The rest of party buffs for about 3-4 rounds.
By this point the aspect of the evil god is summoned, only six cultists are apparent, and the paladin begins strafing and firing arrows. Long story short, paladin and mount are taken out quickly by NPC adepts (only 1 of which gets injured), with one attack from the CR 7 (8? can't remember) BBEG.
Rest of party has split up. Summoning circle fades to a dull (candle-equivalent) glow. The Malconvoker and the cohort Wizard arrive first, both human, and carrying bright light sources. Wizard spams fireball on visible cultists. Hidden 7th cultist (with character levels, CR 6, if I recall right), takes out wizard in 1 round. Malconvoker summons a pair of celestial creatures with awesome well-chosen SLA's, and drops black tentacles onto 4 of the 6 NPC cultists. In 2 rounds, summons manage to Dismiss the "god". Meanwhile, the cultist leader has snuck around, takes down the Malconvoker, and begins to mop up the summons.
This is when the bulk of the party arrive: Full-plate fighter 8 (Capt. America clone), Binder with the summon-full-plate vestige, heavy armor cleric cohort, and medium-armor barbarian finally tromp onto the scene. They mop up, taking out the lead cultist, but letting two of the NPC's escape. Because they can't run fast enough to catch them.
Rest of the session is spent dealing with death, and excited in and out of character discussions re: plot developments, including information let slip by the cultist leader as she coup-de-grace'd the Malconvoker. Once the Malconvoker is up and moving, they are actively engaged with plot developments that his new, hard-won info brings.
[/spoiler]
After this mess, I gave opportunities to shop, pay death tax (even so, party is a tad above WBL), suggested re-training since they could see obvious "holes" in party strategy. The subsequent two sessions have not gone much better.
I have been running D&D since middle school (3.5 since about '04, maybe), and never had to coddle this much just to prevent TPK. What gives??