My mate has had some success with his mono-Seraphon list which is essentially:
2 x Bastiladons
Razordon pack + Handlers
3 x 10 skinks
+ a few other bits (Temple Guard I think to circle the Slann...)
The formation gives you re-rolls for essentially everything and a D3 heal for all monsters a turn with the combined Slann and Engine making it hard to breakdown. Suffers a bit from having to bunker to maintain ranges for buffs so it does struggle to win big in a few scenarios but it's just tough to beat. He's added the Chameleons in recently to help with that what with their popping up but I think the list has legs and it's always a tough game playing against it. It doesn't have any knockout punches but it just grinds you down and, if you play smart with Bastiladons to control board space, can be quite effective against a number of strong lists.
Kroak suffers with the Rules of One impacting his spell so wouldn't recommend him at the moment. Without that restriction he is still very strong though. Depends what style of play you want but I'm not sure how popular you'll be bringing unchained Kroak to a narrative game, etc.!
Skinks, Chamelons and Basties are all good IMO and should be in a mostly Seraphon list to claim objectives and provide some decent long range shooting through the turtles. Hurricanum is just a bit dear currently and, as the best shooting you have is Bastiladons, isn't really worth it IMO just to buff, at most, two units. You might want to consider dropping in some broader Order units but then you do reduce the synergies (which Seraphon rely on) and the flavour of the army by throwing in Kurnoth Hunters and Judicators, etc.
Again, without watering down the Seraphon, I'm not sure Seraphon really have massive punchy units at the moment (assuming playing under GHB as Rippers uncomped are a nightmare!) so you might want to consider a more "grindy" approach when list building to just survive and then wear the opponent down as you heal and re-roll everything.
Just some of my thoughts having played against them, never with, a couple of dozen times now so would be gladly corrected by any more experienced posters/lizardmen.