hmm...hasn't all these been discussed before? about what stacks, what doesn't and if they do, how they stack

Tienhou18 has just pwned Terror's head for 100 gold
 

wah lion win 1 v 4? fighting creeps ar haahha jk jk...i noe u pro ubhm

I believe that by default, creeps do not discriminate against targets except when an enemy targets an allied hero. Only towers will target creeps with the lowest health, normal creeps do no such thing, otherwise those ppl who go for the necro/druid will often aggro the rest of the creeps the moment they attack, which doesn't happen. It is possible for a hero to land ALL the hits on a single creep and kill it in a single wave.  Worst comes to worst, just engage the creep wave minus your own creeps (Or use the extra heroes as 'targets')

In a normal encounter between friendly creeps and enemy creeps, they often focus their attack on the first creep they encounter, regardless of how much HP they have. Besides, creeps and level 1 heroes attack ridiculously slooooow, so recording these values is not as far fetched as it sounds... Heck, they could be really anal and use FRAPS to record the game.