WHFB: Random Scenarios
With 8th edition came the random scenario chart. Before, there was really only one scenario, affectionately known as Battlelines, which is the standard set up 24" apart and shoot stuff until it dies. This was an entertaining scenario that held up strong for many years, but now GW has given us a variety of "standard" ways to play the game. Having a standard set of scenarios to choose from means that you can pick up a game with a stranger and have more options than just killing each other from across the board. Now, when you play a game, you are first supposed to roll on a table to determine the scenario, then roll on D6+4 times on a separate chart to see what kind of scenery that you will each take turns placing on the table. There has been much criticism about this whole process, but give me a chance to defend it, today I'll specifically talk about why you should use random scenarios.
There are 6 scenarios: Battleline, Dawn Attack, Battle for the Pass, Blood and Glory, Meeting Engagement and The Watchtower. Of these 6 scenarios, 4 of them are determined through Victory Points, though they differ in how you deploy, while Blood and Glory and The Watchtower are determined through special scenario victory conditions.
The reason it is important to roll on the chart is because then it is impossible to create an army that is good at one (Battlelines) and not good at any other. Think of this, when you go to a 6 round tournament, if you make your army so that it can win one of the six scenarios, you're going to lose 5 of your games, that's not how you win a tournament. Often times, when testing out an army, people will immediately try out Battleline to get a feel of their army. This ultimately only tests out if your army is good at one scenario.
When you write an army list, consider Blood and Glory as well as the Watchtower in your plans. In Blood and Glory you need to make sure that you have enough standard bearers in your army, otherwise you'll run off the board at the first sight of blood. When you're playing the Watchtower, you similarly need to plan to either have a unit of 20 troops that can old out for a turn or two of combat, or you need to make sure that you have a unit which is very capable of tearing out some defenders. If you ignore these scenarios when you're writing a list, then you will probably lose those scenarios.
Having a random scenario helps to encourage making well rounded lists, rather than taking what is the most effective unit in a straightforward fight. Making sure that you have enough banners to win Blood and Glory, or having an army which can effectively siege a tower means that when you build an army, you have more things to consider.