Yeah I was thrown by this over the last week as I threw into my DPS' macros /target tomb for the frost tombs in UK. But I noticed my DPS didnt switch :/
So what I think Ualaa is trying to say is, your spamming macro on your tank also needs to have the /target <encounter thing>

Please let me know if I am wrong, because I was goignt o be asking this question over the next few days I did down him, even though I didnt kill the tombs, thankfully my healer didnt get frozen :P