Talos and Honsou do not speak for the entirety of their legions, this much is true, but you can see that these legions have their own agenda as well. For example, The Night lords as an entire legion in their persuit of the recording of their lost primarch went searching for it.
But they are hardly united, and many warleaders of the Night Lords were fighting for Abaddon in his 13th Crusade.
The Iron Warriors have paid Abaddon in captured geneseed to remain silent (for the most part) in Abaddon's crusade.
And yet we have mentions of them fighting in Abaddon's Black Crusade in some fairly notable actions if I recall my Eye of Terror codex correctly.
Not to mention Talos has great influence in his legion.
Not as much as you imply. Talos is not the only prophet and not the only one of the Night Haunter's favoured. The fact that he is apart of a dwindling company serving another at the start of Soul Hunter speaks of just exactly what his influence is.
This much is true as well, though as I said this crusade must prevail in order to maintain their support.
Which, appearantly, going by the chaos codex Abaddon has done so.
It seems that the chaos astartes are mastly outnumbered. All they really have is warbands of the first legions and I could only find a few renegade chapters comparbily to the amount of loyalist chapters fighting against them. Who is to say they are at full strength too. The violaters have lost over a third of their chapter of which they will probably never know what has happened to them. The Night Lords for example are suffering from lost numbers and loss of equipment like astartes armor. I can only imagine these rengade chapters and warbands are suffering from the same problems. Theres a point where they will have to look to their well being of their warbands before Abaddon's crusade.
According to Dark Creed the Black Legion outnumbers the Word Bearers 10-1. Only 9,000 Word Bearers showed up in the book, a small part of the WB Legion itself. The Black Legion alone must number 90,000 at the very least.
And Chaos Marines still grow and recruit the old-fasioned way, using geneseed that is not corrupted or loyalist geneseed. The Chaos Codex claims that the strength of the Black Legion grows with every assault Abaddon leads and implies that Abaddon is growing, not getting weaker.
But we don't know how many Chaos Marines are out there still. It depends how big you consider the Legions Pre-Heresy, wheter 10,000 Astartes (Index Astartes) or Visions of War (100,000 as average)
. Pretty true. For game purposes I imagine that GW could have some weird intervention where Abaddon somehow gets weak so they can sell some of the other legions stuff. Probably for the sakes of increasing sales by making new codexs and models. Could see this happening. They would probably do this because you are right in the way that black legion and Abaddon has dominated the chaos fan base and maybe getting a bit boring.
As to how they could weaken him... BL has done some redicolous things. Similar to the Ultramarine pwning, they could have one of the characters owning him in some redicolous fashion.
, like Loken comming out of the heavens and borrowing the "Shard of Erebus."
Other way around actually. What Games Workshop needs to do is buff Abaddon more. (I see more Word Bearers and Iron Warrior armeis than I do Black Legion actually. I'm the only one in my area who plays a Black Legion army. Stuff like Iron Warriors and the Cult Leigons are more popular.)
True or not Abaddon is a ''failure'', or at least has the sterotype. The sterotype is so prevelant it's actually been put in stuff like Black Library with Honsou and Talos. Most people will consider him a failure, even if that's not true. Look at 4chan or Tv Tropes.
Most of Abaddon's Crusades are shrouded in mystery, but we rarely get to see a victory that shows us why he is considered the Warmaster of Chaos. By all means, don't go like Ward did with Calgar. But rather I would like to see GW write up a number of battles for Abbadon to win in order to dispel that sterotyped image of a failure.