Spent hundreds of runs, but was ultimately able to survive for 5min before unlocking the beam (i.e. starting the 5min run before 30:00, ending before 35:00).

You have a small bug (folks below reported it, but without details): if one scrolls the passives tab down to Impatient / Very Impatient, and then click on the Upgrades tab, the Pierce button, even though invisible, is located right underneath the Upgrades button, and also gets pressed, thus purchasing a very expensive (and rather useless) passive ability.
Also, the build I used above to pass 5:00 was: max runes, max mouse, max seeker, max emp, max sword, hp up, thorns, impatient, very impatient. This build passes 5:00 very reliably (I'd say 4 times out of 5). The very same build without Impatient / Very Impatient almost never gets past 4:50. I think something is not quite properly initialized when Impatient / Very Impatient is enabled, making the enemies ever so slightly weaker.
