So far in my games played in WHFB 8th edition I have learned several things. First is that magic is incredibly unreliable (Teclis is the exception here in some very specific builds) Second is the importance of completely destroying your opponents unit. Just breaking them is no good you must run them down and pursue them to get any points. Third is that some basic tactics from 7th edition still apply, specifically breaking through your opponents line and rolling him/her up. As magic is a topic all unto itself and finishing off enemy units is well obvious we will discuss the third thought, successfully breaking through the enemies lines early enough for it to make a difference.
With steadfast how do you reliably breakthrough a battle line quickly enough to keep from having enemy support units getting in the way? One would think that the answer would be obvious. Concentrate all firepower and magic on one unit, reduce its efficacy to the point that a turn 2 charge by cavalry or another fast hard hitting unit can break the enemy unit. However the obvious is not so apparent when faced with multiple threats such as hydra’s or Steam Tanks and large blocks of infantry. The temptation to address as many threats as you reasonably can is very strong. I think spreading your magic/shooting amongst different units is a mistake.
My strategy with an attempted breakthrough is to only target one unit. Depending on deployment of course you want to pick a suitable target. 20-30 should be the model limit of your target and the target should not have any auto stubborn or be unbreakable. The target unit preferably (but does not have to be) should be somewhere near the center of the opponents line. (IMHO this causes more confusion to the enemy general as they have more options to consider when you break through and you have more options to keep em guessing) Additionally you have to be careful with charge distances as they can be significant with a good roll. This is where magic items that give extra movement on the charge are very valuable. Another consideration is that the target unit is not buffed by magic.
Many armies have units that are good at performing a breakthrough; my Warriors of Chaos for example use Throgg and trolls as a breakthrough unit. While for my High Elves it is Dragon Princes or a couple of Lion Chariots. Other good breakthrough units are Bloodcrushers with Herald and +d6 charge icon, (probably want 5 BC and Herald) IC knights with a Warrior Priest, (9 Knights and priest ought to do) HPA’s (yea but what are HPA’s not good at?) Cold one Knights etc…. The main point is that a breakthrough unit has to be fast, hit hard, and not cost too many points (the blood crushers are the exception here)
So now we know what type of target and what type of unit to use how do we execute the breakthrough? First get your unit into charge range of the target and another enemy unit (preferably a high value target) This can be tricky as you do not want to get charged yourself. Angle the unit at the high value target with the corner of your base pointing at the target unit. (make sure you will still be in LOS of the target if it moves. This gets you closer to the actual target unit as well as the subterfuge) Next magic and shoot the heck out of the target unit and while doing so talk repeatedly about how the target unit will not get a flank charge on you when you hit the high value target. Hopefully at this point your magic and shooting will have brought the target unit down to a manageable number of models and your opponent will be thinking of how you are going to charge his high value target next turn. If it all works out then your opponent’s magic, shooting and movement will leave you in a position to charge your target unit. Then charge and breakthrough, once you are in the enemies back field it is time to make easy points from warmachines and other targets of opportunity. Oh and make sure you destroy the enemy unit. If it gets away and rallies charge it again and get those points that you worked so hard for!
There will be times that this works like a charm. Other times your magic and or shooting will fail or the enemies will decimate your breakthrough unit. Not to despair as if the enemy is concentrating on that one unit the rest of your army is free to come across the board. Some of you are saying to yourself, “yea but if we concentrate on one unit as well doesn’t that leave the enemy free as well?” While that is technically correct you will cause your opponent to hesitate or redirect his units when you breakthrough and while you are dictating the pace of the battle and retain the initiative you are winning.