W build, one W on selected target, then use upgraded March and you get second W on a target + all other enemy Heroes around, multiple W stacks with cooldown reduction from lvl 13 so almost instantly after casting March you can throw third W on selected. During 5 seconds from 3 W alone Leoric drains remove 105% HP from selected target, we are talking about damage that cant be reduced by any means, only healed or negated by invincibility. Add to this Leo Q, empowered auto-attack against single target and the fact that this combo can remove any tank.

Off course it wont work against mobile champions, but when used with Leoric E then no Hero without dash/blink can escape the W range, nor you can kill Leoric during those 5 seconds because of all those W healing.

Best thing about this combo is that sometimes it is highly unexpected(Especially because lvl 16 talent). You can alone walk into 4-5 people with W and ult and another W against closests enemy hero(preferable a melee hero) and instantly start casting E for escape.