GM Advice help. Describing details / filling out the battle more.

[SorrySleeping]

I've taken back up the mantle of GM, and as we are 2 months into our campaign, mostly getting into the groove of this again.

One problem I'm noticing, or rather my players are noticing is lack of detail. I try to describe as much as possible, but I don't always give all the details needed sometimes. Two examples from today's session.

Example one:

A large (18) group of bandits is actually a set of cultist that have attacked many caravans in the area and are attempting to use all the materials from the caravans to make a giant golem/construct. They look like bandits for the most party, except for the lack of any weapon on them, due to being spellcasters. The party can see 5 mages clearly concentration on magic but their knowledge rolls only allow them some base info. Four are working on one spell to summon/create something, and one is concentration on a protective/illusion barrier. The bandits spot the party, and take a defensive-ish formation inside a protective magic barrier. The party has seen the bandits and knows their relative location.

The party scout goes through the barrier, attempts to punch the one bandit that is clearly concentration on the protective barrier, gets blasted by magic from everyone inside the circle (making sure to count the effects to the party) and fails a will save, teleporting him back to the rest of the party. Scout goes through again, gets blasted again, but manages to hit the bandit and the bandit fails his concentration check, barrier goes down. Party rushes into to fight the "front line". Bandits have spread out in a circle due to the scout having gone around the entire perimeter at least twice before breaking in, so there is no real front line. One of the party gets mad as he now realizes none of the bandits have weapons, they are all mages, and he could have waltzed right to the back and take out the ones concentrating on spell in the middle of the circle.

Example two:

The bandits aka cultists haven't said a word or anything since the partied has been spotted. The party waited two full minutes behind a hill, thinking the bandits would send scouts or try to get rid of the scout they saw. The bandits are behind and protection/illusion barrier that doesn't allow sounds, smell, and a couple of other things out, but they can clearly see into the barrier without problem.

During combat, there are four people always concentration on a spell, which the party didn't roll high enough to tell exactly what was going on, but could tell it was some kind of creation/polymorph/summoning spell using the wrecked caravans as material. The bandits are throwing bodies to keep this spell going. If one of the ones concentration on the spell dies, another jumps in, sometimes promoting AoO from movement, to have 4 people on the concentration at all times. The cultists/bandits never say a word in front of the party and their clear defined leader is silent as well. Orders were given while the party was hiding in ambush and the cultists knew what had to be done. Summoned golem nearly wrecked the 8 person party (4 NPCs they found, and asked for help from). The party said afterwards that it seemed fishy the spell didn't seem to have significance/the end result was still indelibly powerful and happened "right as they showed up".

I don't want to tell them that their two minutes of waiting and the cultists clearly throwing bodies on the spell without the party doing anything about it, was what made the monster so powerful, but it could have been worse. I was tracking full rounds of concentration for how powerful the monster would get, and this was more of the middle ground for what could have happened.

I know some of this isn't describing as much as possible, but I'm not sure how much the party should be asking or looking for clues. This session seemed somewhat sour for most of the players, and I'd just like to get some advice on trying to steer them in the right direction of things without giving long out of character explanations of things that are going on the the background.

[Hugo Rune]

Sorry, linking too hard on the phone but try googling alexandrian three clue rule.

Basically find as many different ways as possible to throw hints at the players because they will not spot the 'obvious' clues you think you have given them.