Here's the problem with that - if he breaks an outside unit, it's easy for him to simply reform and avoid a counter, unless I'm two or three lines deep. Which is, of course, possible, but that's not useful in scenarios where I have to control objectives spread out over the table or pillage gold.
Yes, multiple waves is among the best solutions. If he reform, you will still be able to charge him in the front, you only need to have in reserve behind the sacrified unit something that should hurt him.
In a scenario with static objectives, you donc need to be the first on the objectives, just to be there at the end of the game, so a slow and steady advance is the tactic to use there. It's even better than a kill scenario, because he cannot just take the advantage in points and then try to evade you, he will have to come to you.
Note that multiple wave doesn't means that the waves have to be the same size. Often its simply keeping *one* unit in reserve in a second line. Against more balanced armies, a regiment of brock rider that you would have deployed on a flank will make an excellent reserve unit, with enough speed to be able to cover by itself several units, and can be kep far enough that it's outside direct charge range and cover the rear of your front units.
Elementals can be another good unit, with shambling + Surge they can make one-turn charge outside the front arc (pivot during the movement phase, use surge during the shooting phase to make contact), so if the fliers try to move over their heads to prepare for a flank or rear charge, you should still be able to get the first charge on them.
Even outside the surge tactics, a stone pirest with bane chant can help you get more localised power when needed, especially if you buff an unit of berserker (on foot or brock riders).
A regiment of brock riders on the charge with bane chant would get 26 attacks on 4+ (so ~13 hits on average) and then wound on 4+ (from TC(1) + CS(1) due to the bane chant) so an average of 7.5 wounds. on def6+.
This should kill even an undamaged soul reaver troop, and put a regiment or dragon at a dangerous level where each additionnal point of damage has a chance to rout it.
The point is however to not rely on any one trick,but to try to combine has many options as possibles.
The brock riders with bane chant is among the bests, but if you combine it with a few canons, a charge by another unit(s) to add a few more points of damage, other units that might charge a flank (he wont kill easily a regiment of brock with their huge nerve but he cannot ignore them eitheir, so put the pression with the rest of your army), it's another story.
Simple rifles (and/or organ guns) are also very good to inflict some damage to def 6+, this usually won't rout them, but can be used to increase the chance that you rout them when you finally charge, or can be used after that to force a new nerve check on a damaged unit.
And remember to use synergy between your different options. For exemple you might keep some elementals units backed by a stone priest or two not too far from your rifles or war engines, so if he tries to kill the ranged units, you just use surge to get a charge even outside your front arc. Even if you charge him to the front after he made a reform, you will still get the first charge, removing their TC for a turn and hopefully doing enough damage to rout or waver it (or at worst force him to retreat)
Also note the option of having a flame belcher buffed by a bane chant for a 18 dice Piercing(1) breath attack.
Any way, the list of your friend is probably among the more frustrating to play against, because where other similar armies would get damaged over time, the vampire can keep healing with life leech, so you need to be able to focus your offensive power as much as possible to wound them faster than they heal, ideally routing them in one turn, and it takes more skill than to fight against the other "trick" lists.
His units however are *very* expensive, so if you can manage to make a good use of your numerical advantage you will win the attrition war even against life leech.