Can you post your build? I just breezed through it on Autistic with my brand new TM cave wizard and have some experience with the game, maybe I can give you some pointers, cannot say for sure though, and if I cannot help you I am sure someone else can.
I restarted with a new character but it was
Str 6
Dex 3
Agi 6
Con 3
Perception 7
Will 10
Int 5
to start, and I pumped all my points into Will. I was leveling TC and TM. Can't remember my feats off the top but I think almost all of them were Psi-Based. I skill heavy into Lockpicking, Hacking, and Persuasion, so no crafting, and I just feel like a shotgun doesn't mesh well with the build. I beat the game on hard with a TC/Psychokinesis Sniper, and I tried to model my build off of that (just switching in shotgun feats for Sniper ones), and it simply doesn't do enough damage for how glass cannon it is. The Sniper build worked because I was able to kill enmies from a long distance, and then use my Psi abilities to peel and deal with low health enemies that were closing in. The shotgun doesn't seem to have the same damage potential for its high AP costs to make it work well with what I was trying to do.
Biggest problem is that you only have int 5. Premeditation is what can glue the two different parts in a hybrid PSI builds since it removes AP costs. My PSI Sniper had the following distribution at level 1: 5/3/7/3/8/8/6. In the current iteration of the game I end up with 12/12 per and wil. This works because the scaling is completely linear. I made some calculations and it was less than 15% damage loss for both disciplines back then when I went for 10/10, compared to the maximum of 16 in an attribute, in those two primary stats. That easily works because Sniper Rifles have such high base damage and extremely strong Aimed Shot and Snipe attacks which can wipe out most opponents that 15% loss is more than made up by a Premeditation TK punch, especially if you set up the proxy first. Imho you should ditch TM and go for PK. Why? Because it has two irresistible stuns with Imprint and Electrokinesis, the Force Field is a life saver, and Force User feat with double TK punch can murderize most opponents. Not to mention against super tough enemies you can use double Implosion to shave off like 60% of their hitpoints. TM for hybrids probably works best if you go for Evasion/Dodge, have ONLY TM and use stealth only for opening. You would not need sky high willpower for that build, just enough to get a decent value. You could even opt to dump will and primarily use the abilities which do not scale or only partially scale with TM skill level. Let me give you an example:
http://underrail.info.tm/build/?HgY...AAAAAAAAAAAAAAMKgAAAAKzkBP2MqwrDCkMKYSw_Chd-_
This is not nearly complete or optimized, I clobbered it together in 5 minutes from my experience with Sniper/PSI hybrid, Assault Rifle user and pure PSI, the tree types I have played most. Basic idea is to use stealth to get into position and blast away, using TM primarily for buffs/debuffs/CC. Since the build won't have LoC it needs something else against stuns at least and Thick Skull is very good there and you can get a metal helmet with shades against disorients. 6 agi for sprint, 6 strength for shotguns, 4 will so you won't get a penalty to TM, though you can live with 3 probably, and 6 Int to help with crafting and get Premeditation, which is core on any build which has PSI, it is that good. 12 perception seems low, but you can further up it to 13 at level 26 with veteran feat and as I said, the damage disparity between max attribute and somewhat less is much less than the value suggests, if it was less than 15% for 10 vs 16 back then then 13 vs 18 is even less, probably around 10%. Imho having such good defenses should help getting up close and personal with shotties. Using PSI purely as support might work better with shotguns as well.
Feel free to adjust it, you can probably get away with not maxing stealth. Rest of the points as you see fit, I would suggest that you try and get decent electronics and mechanics crafting at least, that way you can custom tailor: shotguns, cloaking device, energy shield emitter, taser, googles, psi head band. Basically everything but armor and feet slot. You can opt to get 45 into PK for Force Field, Electrokinesis and Imprint for some more irresistible CC.
I have seen some people opt to go for 75 in TC for LoC. Imho TC is one of the few disciplines which are all or nothing. All of its abilities rely heavily on having a high value in TC to overcome enemy resolve at a very sucess rate. Just getting 75 points into for LoC is a bit of a waste, with that many points already sunk you should go all out. Though for this variant with such low will you would get too many resists on TC CC. If you really want TC you have to dump con and up will, though 10-12 will is usually just enough to get through.
Check out sebas post before mine, some nice info there.
Shotgun actually has feats you need to get, and a lot more of them than sniper. So 5 Dex, 9 Per and 7 Agi are the stat baseline for any shotty build imo.
Realistically I think you can only build it with TM since it only needs 3 Will, 70 effective skill and 1 feat to get going.
I would say a good starting point is:
str 7
dex 5
agi 7
con 3
per 9
will 3
int 6
But what I don't know is what to do further. Will shotty do enough without further pumping per?
Pope Amole II - since the other builds are done already, shotty today? :D
As I mentioned earlier, when I did damage comparisons, or rather damage modification comparisons of skill levels, my Sniper lost less than 15% of his damage at per 10 vs 16. I guess you lose slightly more due to slightly lower hit chance, but that is easily rectified as a sniper with scope and/or bipod and of course you always have 95% against stunned/incapaciated enemies unless you are at extreme range and/or lighting modifiers screwing you over without night vision or light source next to target.