Well, I am still not taking great weapon marauders, so that point is irrelevant to me.
As for flails, giving HW/S in addition would be nice, s5 during the frst round and then having a 5+/6++. But with that setup you will be really expensive. Ok. So no then - a 6+ don't cut it. As Tim said you can't switch weapons mid combat so its irrelevant.
On shield marauders, yes. I haven't tried out marauders too much in the new book as I'm using the flashy new monsters and frantically playtesting everything so I can review it, but 10 points for a marauder with a 5+/5++ isn't terrible. .....4 more points buys you a extra T S I WS and A, and a +1 to your armor save. So yah in the book its in its a bad idea.
And to be honest, marauders are still good and competitive, just priced in with the options in other books. What other armies? Empire, Ocr, undead? Each is a separate army priced appropriately for the other units and special rules they contain. You may have a point but without supporting evidence or examples this is a meaningless claim.
Luke - they are more expensive, but I think it is totally irrelevant because the new price is the new price. You are spending more for the same, or the same for less, but it isn't like you can still buy the old marauders. Yah hence why I don't take them anymore in competitive play If TH/SS terminators cost 50 points, less people would still take them but they would still be taken often enough. You say that now, but I know for a fact that if they did suddenly increase in cost we would see a 50% drop in them showing up at tournaments immediately, hell even now they are less common as other options become more attractive. Marauders are in a similar boat. While there are now more cost-effective options, or options at least closer to them, they are still decent and priced with other options. Ghouls are undead, halberdiers/swordsmen have detachments and wargear thats why they cost 7-9pts. Does this make sense? I understand where you are coming from, but comparing an OP old option to a watered down new option doesn't really work. The argument has nothing to do with the old book and everything to due with common sense paying 2pts to upgrade a chaff unit is pointless as they are there to use steadfast and nothing else, especially in a army book where T4 S4 WS5-6 is the norm. So no regardless of anything else buying armor and shields for marauders has always been a bit of a bad idea in 8th.
And I would still give a tzeentch anvil light armor and the mark for 55% survivability against s3. So would I, but mark of nurgle with no armor or shield is probably better as it helps regardless of the enemies strength, mind you they then become more susceptible to ranged fire, but considering they are in units of 40-50 and only would have a 5+ save realistically how many more marauders would that armor save over 2-4 turns?
See the problem with your point is its one of those its a decent unit arguments. I am simply arguing from the competitive side of things, and with the current points costs upgrading marauders at all it typically a waste of pts with a few exception.
Also you completely missed the point of my argument which was that at a certain points costs units become cost ineffective for the army they are in, and 8pts for the equivalent of a empire trooper is dumb in a army that offers warriors and monsters that can easily fight 6 times their number in empire soldiers. I mean we have all seen an idiot or two at a local gaming center that consistently loses game after game because they thought it would be cool to upgrade a unit until it was 35% of their entire army, only to find out they died just as fast or only put out mildly more damage then they would have otherwise. (Large units of paladins comes to mind here)
In friendly games to mildly competitive ones I do see some uses for certain marauder unit builds; even in 8th. For example here are some builds that I would consider using in a casual setting.
-35 marauders mark of nurgle, full command
-20 marauders fails, command (Use them on the side to destroy weaker outflanking units)
-40 marauder, full command (They exist to hold up unit, and nothing else and with LD8-10 with a nearby BS they should stay put even if they get 2 full ranks stripped each turn).
-30 GW, command (Less effective then the other builds, but should still be enough to scare of other chaff units with their Str5 attacks)
Marauders are a decent enough unit for 8th, but my point is that you shouldn't use them expecting to win combats or kill units as they can rapidly become a point sink (So most upgrade options end up handicapping your force when taken in large numbers). After all they more or less occupy the same place they always have, only now the actual combat effective builds are to pricy to be worth it in a army where costs can be so high that even at 2500pts you may only have 45 models on the table.
The perfect example of this phenomena was what happened in the VC army last edition. We saw this in how there was a mass phasing out of skeletons in favor of ghouls. The reason was a simply a difference of 1-2 points. As the ghouls came with so much that buying a skeleton for the same price was dumb in tournament settings. See every new book has a almost dedicated horde style units, and the difference between a valuable asset to your army and a fun unit that should stay out of tournaments is typically only about 1-2pts most of the time. To put things in perspective marauders aren't equivalent to swordsman, or ghouls they are the zombie/clan rats of the WoC army, and with their high cost its not really worth taking them with anything but a hand weapon and a t-shrit.
Disclaimer: I actually like the WoC book, but like all books certain units, and unit builds should not see tournament play, unless you are deliberately trying to handicap yourself.