ThorChild: Going on comments from other places and here it does sound like they have upped the sentinel's aggression. And also the 'difficulty' has a big effect also, so it looks like HG responded to some feedback or their own playtesting and decided the sentinels needed a buff.
I'm still waiting on a few more patches before diving in myself, but at least i will go in eye's open so to speak and pay more attention to the sentinels than i used to!
Definitely juiced the Sentinels. No more drone mining. :-(
The patrol drones much quicker to investigate activity but to compensate there are now "drone alert" indicators in your HUD, so that's a help.
The two drones in the first reinforcement wave are armoured and you need to destroy that shell before getting through to the drone itself. Effectively you have to destroy four objects, two of which shoot back.
There is no longer a countdown timer "wheel" to show when the next wave will spawn. The first reinforcement wave stays on you until (a) you die, (b) they die, or (c) you break contact well enough and long enough for them to quit looking.
(c) is the preferred outcome. If (b) then another, stronger wave swoops in. Repeat the options until you can get away from them. Option (c) is the only survivable outcome, as far as I can tell.
I don't know what happens if all of the level 5 sentinels are destroyed; they may just keep spawning forever. There is no more "kill the drones and the one walker at level 4 and then all the sentinels stop spawining on that planet until you reload a save or leave."
The barrels which the drones drop contain rounds for the boltcaster and power for your personal shield.
Jump in, the supercooled liquid which looks like water but it's at -65C is fine!