Never try to compare SR to DnD, the mechanics are so different, there is nothing to compare.
In DnD, whenever you reach a certain amount of XP, your character grows exponentally. (You gain HP, you gain better saved, you gain better attack bonuses, you gain feats.) And so, the game gets less dangerous as you progress. At lvl 1 a warrior has 12 hp. (For arguments sake) meaning a long sword hits him twice, he's dead... at lvl 2, he has 24hp... so that longsword has to hit him 4 times to kill him... at lvl 5 he has 60hp.... now that longsword has to hit him 8 times.... and so on...
In SR there is no lvl system, there is a karma system. Karma is used to improve everything, with progressively higher costs per improvement. Generally a character has 10 health boxes at start (average). A 100 karma later, he could still only have 10 health boxes (and 100 karma is roughly 12 to 15 runs in!)
That, combined with the damage of most weapons (a light pistol does 6 damage!) Means you have to be careful and can't expect to take as many 'hits' as one expects in DnD....
In fact, getting shot twice can kill many people!
So yes, your buddy is correct that SR can be brutally deadly. The good news is, careful planning and a wise array of gear and options can increase your life span. (Provided you get yourself out of DnD mindset of 'charge the enemy, hack him to bits).
What he is NOT correct is that missing an element of team (decker, sammy, mage, bozo the clown). First off a fixer is not going to hire a team that can't handle the task - his rep is on the line! He needs the team to succeed to continue to get contracts throw his way... So he will carefully match a team to a job.
No awakened on the team? Then the fixer isn't going to give you a job that requires an awakened to succeed. He's going to look at the team and match their abilities and competence to the jobs he has.
A 'perfect' team will gave all the bases covered, but 'perfect' teams are rare! (Heck, less then 5% of world's population has magic potential, even less have developed that potential, and only a tiny fraction make it to the shadows! There is plenty of work for all types of teams out there.
●●●●
In other words, a good GM tailors to tuns to the team do they have a goid chance of 'winning' - if they play smart. (All best are off if you play like idiots)
A poor GM will club you over the head for 'poor character choice' (IE: not making a balanced team, dispite players not wanting to play a certain archtype).