Not really, you face different strats, four in Legendary, for example, but you could deal with them.
Check this:

https://youtu.be/L_YWfO9rhmc

About myrmidons, weak spot is Torso, you can use also explosives, fire...

Myrmidons/Worms is the easiest strat to deal with, because you have a whole full turn before they can act and you can do a lot of things to them. Unless some really extraordinary circumstances I definitely wouldn't touch the reactor for them.

SOP with Myrmidons is just disabling their torso, but as they bunch up on deployment you can also nade them; it will bring part of the balcony down, but it can be worth it.

I realy do not prefer these base defence missions either. When I played it for the first time I imediately switched back to vanila, because HELL NO, THIS SUCKS. I know that base defence missions in vanila are maybe to much easy, but Pandorans are conquering entire world and it is in the end at least your base where you have the upper hand. I would prefer if there could be something in mod setting to switch this back to normal, like there are these limited deployement and more mist omens switcher.

Yea base defense missions are nightmares now. It turned into a savescum fest. I've had minfraggers run straight through fire without injury and fire grenades dont stop the 3 umbras from rising up right next to my guys.

Only way I could pass the mission is by putting everyone in the lift on mission start and huddling my guys up on the balcony above the sentinel. This is my base, you'd think I'd have the upper hand. At least on the balcony/upper level the dozen worms and mindfraggers cant get me.

Originally posted by Muton:

I've had minfraggers run straight through fire without injury

Are you sure that's what happened, i.e. they stepped on tiles in fire rather than walked around them? If yes, that would be a bug that I haven't seen before. If that happens again, please post your Player.log and TFTV.log on our #bug-reporting channel.

Originally posted by Muton:

and fire grenades dont stop the 3 umbras from rising up right next to my guys.

Fire only stops umbra from spawning if the 'host' dies from fire damage.

Base defense is meant to be a challenging mission on higher difficulties, especially Legend and Etermes. You have different means to prevent and/or to prepare for it; that's your upper hand.

- Attacks can only happen if there is a Pandoran Colony close to your base; the closer a Pandoran Colony is to your base, the faster it will prepare the attack.
- Pandorans prepare their attack faster vs Bases in the Mist (so building a Mist Repeller helps).
- There are researches that can help you: Walls of New Jericho gives extra time on the meter and Project Domovoy reduces the rate at which Pandorans prepare their attack.
- The base defense mission layout is the one of the base, so you can build facilities with that in mind.
- You can build security stations, each providing 3 guards that are great at dealing with smaller threats.
- You can keep a squad somewhere in the vicinity of the base to respond before the base defenses are penetrated/the base is infested.
- Before deploying, look at your base layout and make a plan. If you have tactical advantage (the Pandorans start at the entrance), consider whether you want to defend the entrance, or lure them in and ambush them in the corridors. Yes, worms and myrmidons may assault the Hangar. But do you need to be there? Maybe it's far enough from the entrance that you can leave them there. Remember: your objective is to survive for 5 turns, after that there will be no more reinforcements and you can mop up. If the Pandorans have already infiltrated the base, focus on quickly destroying the objectives, as that will stop further reinforcements.
- Don't forget you can use a console to stop a particularly nasty wave of reinforcements.

If you still feel like it's too hard and you are not enjoying it, just go the main menu and lower the difficulty on Tactical for that mission.

Well on that mission, the sentinel was in a large area, surrounded by like 8 eggs and tons of enemies..I couldnt run 4 of my guys out of the entrance on the other side of the base fast enough to escape all the enemies, then 3 umbras showed up and killed me off. I reloaded and put everyone near the large area with the sentinel and kind of barricaded my guys in the upper floor of one section.

On my second base defense, it was a bit easier. I threw fire grenades at the choke point and ran everyone to the end of a corridor and hunkered down with overwatches.. Still difficult. For some reason there was no sentinel that I had to rush to kill. I'm playing Hero.
I had 10 soldiers and a vehicle at the base but was not able to deploy more than 8 slots.I was hoping since its my base I could defend it with everything I had.

I'm also having a serious problem with Synedrion. They are at -6 diplomacy. Some of their havens got destroyed, few left, so when I defend the other factions bases I keep losing their favor. Not sure how to get it up to 49 from here. I've never really had this problem before in my other 10 playthroughs. I guess I'll have to go on a sabotaging spree. I'm really needing their tech

You should have 9 deployment slots for a base defense (but there is a VO with -2 and one with +1 slots).
If you start a base defense early (I think more than 12 hours left) you will get the “easy“ one. “Hard“ is with Spawnery and a couple of Sentinels.
Re sabotage missions: a spree takes time as there is a cooldown of 7 days.
Re other means of getting faction tech: buy at the Marketplace, reverse engineering things, play more Lair and Citadel missions and eventually get the reputation up.
In general: TFTV has “Harder diplomatic penalties“. I think on or off has to be chosen on a new game start. It is ON on Veteran and above. I like it.

7 days? My god I'll never get there.

A spawnery in a base defense? TWO sentinels? I've only seen one sentinel

One Sentinel is a medium defense. A hard one (=timer has run out) is Spawnery + 3 Sentinels.

Ahh ok.. I'll do the mission ASAP then

Does repairing damaged structures at havens increase diplomacy score? I'm desperate to increase Synedrions affections for me, at least to 49. 74 is hopless. If Synedrion attacks anothers haven is there a way that I can assist them rather than repel their invasion?

My recommendation: forget about Synedrion and do a different ending. (In my current Etermes run Biogenesis spawned in Antarctica. Still currently unreachable while I have reached 100% with NJ in the 5th week.) What is the Synedrion research you absolutely want?