Finished it the second time now. First playthrough (on normal difficulty) was with lot of hacking. For my second playthrough (on Deus Ex) I ignored hacking pretty much and went for stuff like punching through walls, lifting heavy things and jumping very high. I noticed that hacking is not necessary to complete the game. Not at all. The handful of cases I really had to hack were lvl 1 locks. For pretty much everything else I could find the access codes or passwords lying around or ignored it. If I stood in front of a lock I couldn't hack, there was for sure some hidden air duct that allows slipping past. Towards the end I still put some points in hacking, since I didn't have anything else to put it into anymore
After playing it both as Sam Fisher and Robocop, I am impressed by how different the playthroughs were. Some people lived and died differently. I found some side-missions I overlooked the first time and the bosses were laughably easy once I found the rocket launcher
Thinking of playing a third time, this time without killing anyone...