Sherro is definitely more experienced than I am, but here's my opinion on the on-season rugby training:
On-season training is generally for you to maintain the strength you gained in the off-season, not to actually get noticeably stronger. I'm approaching my own rugby season and this is what I did for my off-season, season prep, and what I will be doing for my in-season training:
Off-Season (Westside variation, a lot like WS4SB, but RE day is heavier and exercises are different) - after a week deload after the season, I jump right into this, usually doing a 4-5 week cycle followed by a deload week and repeating that (deload weeks are essential, if you feel like you're being lazy, do a bit more conditioning, but don't overdo it)
Mon ME Squat/DL
Wed ME Press
Fri RE Squat/DL
Sat RE Press
If you want specific exercises, I can write it out but basically this is what I did:
Monday - deadlift alternated with box squat each week, 3x3 (80% of working weight, 90%, 100%)
Wednesday - flat bench press, 3x3 (90%, 95%, 100%)
Friday - back squat 3x5 (80%, 90%, 100%)
Saturday - standing barbell press 3x5 (80%, 90%, 100%)
Each day I did 3-4 assistance exercises (hams/lower back/quads/abs on Squat/DL days, shoulders/tris/upper back on Press days). Conditioning stays at a moderate intensity. The goal is to stay in decent conditioning shape. I'll switch things up between running (steady, intervals, hills, etc), sled drags, farmer's walks, car pushes, and hitting a tire with a sledgehammer. As a guideline, if you have significant DOMS, you probably did too much.
Season Prep (again, based off of WS4SB) - two 4 week cycles with a deload week in between cycles and after
Mon ME Squat/DL
Wed ME Press
Sat RE Press
Here I replace the RE Squat/DL day with a extra conditioning workout and all the conditioning workouts get more intense. I make sure to run for one of the conditioning workouts at least once a week, if not twice. The other conditioning workout gets more intense as well. I want a prowler to push, but I've been pushing my car which works as well (just throw more shit in it to increase the weight). The weight training stays the same, although I progress slowly (2.5 lb jumps instead of 5 lb jumps, don't progress on assistance exercises - this is me purposefully doing that so that I can keep from getting burned out, I'm not a gifted with great genetics so I have to be careful).
In-Season - the length of the season, you obviously can't take a week off in the middle of the season, but you could stop weight training for one week if you're getting fatigued
Mon Squat/DL - practice
Wed Press - practice
Workouts consist of a squat (on Mon) and bench press (on Wed) for 3x5 with 5-10 less than your 3x5 best from the season prep. I will add weight in 1-2 lb increments throughout the season, until I've reached my old best, then I drop back down to the start. Remember the goal is maintenance. I'll do only 2 assistance exercises (squat - posterior chain - abs, and bench press - military press - upper back) and keep overall volume low.
I have a friend who's a rower (again - not a elite rower like Sherro's, but the info might be helpful). He basically focuses on getting these 5 exercises stronger: deadlift, front squat, barbell row, high pull, and overhead press. Assistance stuff he does include: back raises, good mornings, reverse hypers, leg presses, dumbbell rows, upright rows, and flat-incline dumbbell presses. I don't really know his program exactly, but that's what I've seen him do and what he talks about.
If your coach has you doing all the pulling and leg work you need, and then just high rep circuit pressing work, I would say go into the gym once a week and do the following workout:
Bench Press 3x5 (straight weights or 80%, 90%, 100%)
Military Press 3x8 (straight weights)
Triceps or shoulder exercise 3-4 x 10-12
Also, in your free time I would do a bunch of shoulder and hip prehab work. If you're doing high rep light weight cleans and leg presses, it doesn't seem like you're getting much hamstring/glute work. There are a lot of articles on here for prehab and rehab work, so check them out. I might throw in some GMs, RDLs, or pull-throughs (3-4 x 8-10) at the end of you lower body workouts if you haven't done any exercises for your hams/glute/lower back. I doubt your coach would get mad at you doing that - he might even he impressed at your hard work.
If you do this extra workout you MUST eat more (which you should be doing anyways because you said your goal was size and strength) and you MUST sleep more. You're adding in an extra intense workout (albeit a short one - you should be in and out of the gym in 45 minutes) and you'll need the extra rest.
Hope some of that was helpful and I wish I could help more on the rowing.