Singing spears are better than fusion guns vs tanks at range >6, no question. Singing spears also tend to be quite good vs Monstrous Creatures as they wound higher toughness levels with greater frequency. Unsupported it is a unit you can afford to discard - I'm used to fielding 4 though, which will generally require 6 wounds to bring down. Their greatest asset here is that they can tie up something you'd rather not deal with just by deploying in its way.
More importantly, I've been getting more "shooty" in my approach, and it is imperative that my aggressive units not get caught in close combat with the enemy for a long time. Once this happens my shooting units have no targets and their firepower goes wasted. A seer council getting gnarled in combat by several enemy units at once gives all those units a springboard by which to get closer to my lines, and if fortuned is likely to merely restrict my own capability to shoot.
The units I want to make resilient are my troops choices. Other units merely have to kill stuff as dead as possible, as quickly as possible.
Also, 1 heavy flamer != 4 heavy flamers, especially when the target is doomed. There is no comparison. And for me, non-transports are not too big a threat because they are easy enough to silence; it's far harder to keep a vehicle from moving and the stuff inside it is almost always a bigger threat. Killing infantry is therefore far more important.
Fire dragons are good and have their place in a list, but "suicide" units, when used properly, can change the whole course of a game. In 5th I pretty much always plan for one or two units that are disposable in an army list. Think of it this way, everyone is trying to cut back on their KPs but few units outside of marines have the ability to split their fire [marines do so with combat squads, but this also inflates their KP count]. This means an enemy army will have units that can put a massive hurt on a single target a turn, maybe 5-6 such units plus a few others. The problem is that unit's gonna dump the same amount of power into a ten man warlock squad plus eldrad plus yriel as it will to 3 lowly warlocks. And that's it for their turn.
Sure, the uber council, wraithguard, and etc may still be standing afterwards, generally to get assaulted. And then on my turn my guns sit idle while the enemy force consisting of 4 nob biker teams finishes my squad off, and on his turn he now has free access to everything.
Instead, I put something up front that's damn well gonna break, and hope it does. And my guns are staring the enemy in the face as soon as they break down my wall.
Keep in mind though, this is in reference to shooting-oriented lists, which I'm switching over to because honsetly it's too hard to win the combat game reliably. I keep one or two such squads for the late game if possible, and otherwise it's scoring and shooting.
