Just a few notes from an old-timer, though this might be better posted in the Final Product thread:
Replicating a similar Pokemon in function can't really be classified as a failure. When you have 400+ FE Pokemon like 5th Gen has, there's bound to be some similarities to other Pokemon, even if it's only inclusive of the 50 or so things in OU.
It's also not bad to have a Pokemon with clear weaknesses and drawbacks. You don't necessarily want something that can perform offensive and defensive roles equally, as that may make it overpowered. I imagine if we ended up giving Mollux Agility comparisons to Cloyster might be made instead, though Cloyster has a decent level of coverage and Mollux doesn't, on purpose.
In general I'm heartened to hear Mollux described as a Tentacruel / Heatran fusion, since it says to me we've built an effective defensive Fire-type that can fit in on many teams because of its unique typing / ability combination and raw offensive ability (Heatran is a particularly acute comparison, as without its Fire Immunity from Flash Fire, Fire/Steel would have some serious problems with a lot of OU, and Heatran in the sun would be far more difficult to use).
All of the sets I've used and seen to be effective always have either two-attack coverage with Recover or are entirely defensive with a single STABbed option to ward off opposing walls. In general I like it because you can't just slap it on a team with any item and watch it rampage, you have to use it intelligently and make it work with your team.
One comment I did find interesting would be that Tentacruel wants its typing. I don't really think that's true, the SR/Rock weakness in exchange for the Electric weakness along with its STAB being neutered rather than enhanced by rain would leave Fire/Poison Tentacruel wanting. They have a similar set of skills but they perform different roles for a team.
In general I still think Mollux has bad typing, but Dry Skin alleviates its biggest problem in dealing with Rain, letting the strong points of the typing shine. I also think the stats really helped out - it needs the strong offense and passable speed, I don't think a Fire/Poison Tentacruel with the same movepool but Tentacruel's lacking offensive stats would have been nearly as effective. The ability to force out Ferrothorn before it can ever lay a hazard, even in Rain, is crucial.
I'mma still say project well done, heh.
[17:53] <&Deck_Knight> If I Cite and Prune CiteandPrune's post, what does that make me?
[17:54] <Birkal> a citeandprune cite and prunner
[17:54] <%DHR> O_o lol
[17:54] <+Mos_Quitoxe> Cite and Prune doesn't do enough of either
[17:55] <+Mos_Quitoxe> can we make him change it or force him to pay damages
[17:55] <&Deck_Knight> It would be a lot easier for him to Cite and Prune if we made him a mod.
[17:56] <&Deck_Knight> I delegate this task to Birkal.
[17:57] <Birkal> >:|