It's probably best if we look for the shortfalls of Vampires first. Well, taken as an individual model there is only 1 shortfall that springs to mind and that's the limit to weapon and armour choices - no choices are available at all in the basic profile, the Vampire just gets a single hand weapon.
However, you can still equip your Vampire for combat by spending points on Vampiric powers. You could for instance make the Vampire an Avatar of Death for 20 pts (this gives the vamp heavy armour, a hand weapon and shield or 2 hand weapons or a great weapon). This is your best option if you want to tool your Vampire up for a fight but don't want to have your Vampire lead a unit of cavalry.
Alternatively, there is the Dread Knight Vampire power a more costly 25pts but you do get a barded knightmare, heavy armour, lance and shield (pretty good value for money in my opinion)**
** the barded knightmare provides a strength 4 attack (benefitting no doubt from some rigour mortis stiffened sinews !). Most horsey type mounts only attack with a strength of 3.
The good news is that both of the above armour and equipment related Vampiric powers still leave you with enough points to choose other Vampire powers worth having (I will summarise the Vampiric Powers in a later post)
The other main drawback of using Vampires is their impact on your tactics. If you want a magically effective army (this can prove expensive) then you will end up taking a lot fewer core unit models than you might othwerwise do. This being the case, you really need to ensure that your Vampires can raise additional skellies, zombies, ghouls etc. To be sure you need to invest heavily in magic, vampire powers and bound spell items to be certain your enemy cannot ruin your plans with dispel dice and scrolls.
This needn't be a downside to Vampires though because you can choose to make your army all combat related and treat your Vampires spellcasting ability as a nice to have bonus which may sometimes work and sometimes may not.
Vampire Counts Hero Summary
Vampire Heroes are great, which is just aswell because your army must include and be lead by at least 1 vampire.
When taking Vampires either make them combat orientated or concentrate on magic. Trying to do both and to cater for all eventualities probably will not work. A strong magical force or a strong combat force should be able to cope with any enemy before you***
*** if you know you are facing High Elves or Lizardmen then stick with a combat focus. These Lizzies and pointy ears are all too good at shutting down the magic phase.Image is © Games Workshop Ltd. All rights reserved. Used without permission.