For Aurora. (using heroes here), I usually grab the first crystal by the guardian where you come in, run to the far 'spot' and place the crystal. I plop the heroes just a bit farther south (closer to where the enemies are coming in) and then KILL THEM ALL, targeting crystal runners first...when all the foes are dead, grab the crystals from either spot (I usually have to kill the boss so I just take the crystal from there). This works for both nm and hm as they will try to nab that crystal spot first--so all you need to do it kill all the enemies first.
( I usually take a mm, sos, fire ele, healer with me in both modes, in hm I add another hero depending on what my profession is).
For palace I grab danika and the tengu to come with me, I would also take an sos rit if you are playing communing. I also use eye skills like ebon assassin and pain inverter to help with the harder foes (and pi on the bosses---specially the ele boss!). '
Cant really help on killing Shiro as the wiki has the best solutions for that (and I use them usually).