Nope, definitely not harder. It was rather easier in the phases you mentioned.
One thing I noticed though was that Liquid Hell in last phase targets the OT often, which makes it a bit harder for us who's using a single tank strat. and a Dragoon tanking the hatches or the God / Goddess of RNG just trolled us. It happened 3x in a row in our run, and cleared it at 4th.
