I hate giving sensible answers in the NAAFI.....
What you have to remember is that there are 2 types of hierarchy, explicit (grade, job, position) and implicit (how long you have been there, reputation, and the strength of your network). You're issue is with the latter. Having only been there 4 months your boss is going to be in the position of thinking:
Chogi: been there a long time, knows his shit, has cards to play (race, length of service) that could land me in a tribunal if it goes chebs airwards, knows everyone and knows the system;
Deanol: been here 4 months, knows his stuff technically or I wouldn't have hired him, still in probation so no risk if I mag to grid him, can already see that he's calling out Chogi on being a waster, not had time to establish relationships and a support structure around himself.
See your vulnerability?
The fact is your boss may know Chogi is a waster but could be, because of all the reasons above, hamstrung when it comes to doing anything radical and Chogi knows it. Calling out Chogi is, in a way, also shining a light on your boss' powerlessness to do anything to hoof him (he would have done it by now if he could). It may also be that while Chogi is slack in some regards your boss just can't afford to loose him because it will take time and money to replace him and Chogi is keeping at least the main stuff he needs to rolling which is keeping the development on track.
The fact is, frustrating though it is, you will have to find a way of either working with Chogi or working around him otherwise you will quickly be the square peg in the round hole and the irritation your boss can live without. Being right and being employed are not the same thing!
I've found there are 2 types of people "masculine" and "feminine" and it's got SFA to do with danglies. I've worked with plenty of women who have the masculine traits of problem solving, directness, leadership, and integrity. I've worked with and for men with the feminine back-stabby P-A traits of a bitch. Chogi is the latter and he will scheme to undermine you if you expose him for being a lazy waster and he will manipulate everyone to be on his side because people like him instill fear of consequence in others, and he will use the natural sympathies of his networks to turn people against you. Don't try and do what you think is the right thing and point out his failings, stay out of his way, be professional, and if you need to escalate something because you genuinely need what he is not giving you then a quiet word with your boss and leave it at that.