It's my first ever post and a long one too so apologies.
I have a few points to mention that others have touched on already. I have played a lot of the Descent Scenarios and finished a RtL campaign a while back. The problems there were the dungeons and encounters not staging up per campaign level and obviously the final battle (beastman Avatar) being a walkover for the heroes as the beastman got 1 attack in (which missed) before he and his 2 clones were wiped out.
I was happy to see these imbalances were addressed in SoB for the most part but playing a campaign in which we've just hit gold level, the OL is being nice to the heroes becuse the game could have been ended long ago at this point.
1. Captain Bones Avatar took Death Head upgrade as the first action in the game. Suicide bomber skeletons do stupid damage to copper level heroes. This was compounded by Hordes of things being in play in many dungeons.
2. The heroes got pwned in the first week as they thought to leave the island straight away and suffered a total party kill right off the bat. This is a huge issue combined with the above because we're on the Shadow Queen plot so, week 3-4 saw the introduction of A New Law. Without ready access to fatigue potions, the heroes can't fatigue into battle so easily and for the rest of the game are slower in each and every dungeon (preserving their fatigue as much as possible). This can make them even easier prey for well placed suicide skeletons on a clever set-up.
3. In the hope of getting better weapons and xp to upgrade the ship, the heroes hit dungeons looking for decent treasure and a few potions. In the interim they allow the Siren to place a siege. Tarianor, should be the first to fall. It has low defense and no dice training in Fighting or Subterfuge. By the time the heroes see the benefit of Alchemist 8 during a New Law scenario, Tarianor is gone as is the access to Shark Tattoo. All future sea encounters become difficult.
4. Finally in relation to sea encounters, The heroes have gone out twice to tackle the Kraken and break a siege. The first time was in The Wild Vortex. Shot a tentacle and Webbed the Kraken before the current pulled them onto the rocks (second turn) and gave away another TPK. Second attempt directly after took place in the Dire Straits. This went better. The Kraken got webbed again, All the tentacles got blown off it BUT, with no sails and 4 attempts to drop anchor, the current still had the party "flee" before finishing him off.
We're now at the start of gold level and the Siren and Kraken are wandering artound together doing nothing. The heroes are incapable of defeating them and if they sack another city the game will end so the OL is just playing it out till the final battle for the heck of it.
Also worth mentioning that the OL is so far ahead of the heroes that since near the start of silver level, each hero is worth -3 conquest.