Higher phase count isn't always the best thing to go for. Especially when playing for fun. But even still, I'd argue a high phase count is a two-edged sword, because many times getting this number means you have a lot of models in your army who aren't pulling any weight.
In a lot of larger lists you can still phase a cron player out in few rounds because their phase number is too high. Sound ridiculous? Think about it:
Say you have 3x15 warriors, 3x5 destroyers, and a Lord with an orb somewhere in the heart of the phalanx. Just to get an example of a list with lots of crons [61 here plus whatever else]. That means the enemy has to kill all of your warrior teams, or all of your destroyers and two warrior teams, plus the lord in both cases.
A squad of warriors is pretty easy to catch, since they have short range and have to advance to score in most missions. A squad of warriors receiving a charge does 15 attacks, generally striking last. To give a favourable example, a squad of striking scorpions [10 plus exarch, which costs a fair amount less] slams into them, dishes out 36 attacks, 18 of which hit, 9 of which wound, 3 crons die. The crons strike back, hitting 7.5 times, wounding 5 times, and killing two. Now the scorpion exarch strikes, and kills another 2 crons. Combat one by 3 for the Eldar, without doom, fortune and etc.
Imagine 3 such scorpion units doing this sort of things, you're hoping you pass those tests because otherwise 10 crons get swept from each unit and aren't getting back up no matter what, another 6 need the resorb to do so, and the remainder may not survive/have no one standing to rejoin. That's phase out. With a phase point of 15. You could go higher, but 45 warriors is 910pts. the 15 destroyers are another 450. A lord or two is another 3-400. That's pretty much 2k and the only game you've got by doing it is a shooting match.
I don't think the list posted here is viable for competitive play, but it sure looks like fun and there's several good tactical options available to it. You need to consider the person's playstyle and what they're going for. The scarabs are one of the better choices for the bug-zapper lord since they have so many wounds.
