Slayer is a fun method to train melee stats so if you plan on going through training, try it. It's a good way to break from the monotony of RS gold training on a single monster. Someone who doesn't have 85 Slayer, Abby whips are only 1 in 540 not killing 125 people camping. And the biggest profit from slayer doesnt come from the huge drops, it's the little ones adding up over time . Along with clues to follow if you take it and you're well-organized herb runs during your work.
Yes, I do not have 85 slayer. However, that doesnt mean I don't know anything about it. There have been reports of having no whip drop in 4-6 hours of endless killing. The fact of the matter is that it's one of the rare drops. Any help website you visit will mention the whip as one of them.
The odds of getting whips within a 75-125-125-kill range is feasible however, it is not tipacal. However, it is possible. It is more likely that you have a chance of getting it within the 1-540 range. However, you might not get one. If you ask someone why they train slayers, they'll tell you that it's always because of the huge drops. For example, whips from abby deamons and sol from ice strykewyrms, etc.
If they are able to get the drops, most of their revenue won't come from them in particular on ice wyrms as they can drop amazing amounts, the SOL is merely a bonus. The 1/540 figure is from the average dropping (mite be 520 but I'm not sure) but it is due to players submitting the number of kills they require to obtain a whip. it is possible to find the range you want, but this isn't a drop rate.
Helm of Neitiznot is a fantastic balanced helm, go for Verac's/Torag's helm if you want more defensive stats or a Fighter hat to increase offensive stats (about equal stats with the Rune full helm but with bonus points in Crush, Stab and Stab, Slash and Crush attacks)
Guthans Plate - decent the Fighter torso has an attractive Strength bonus, so it's an excellent choice when you're unable to afford Bandos; also I'm not completely certain about this, however I'm pretty sure the Torag (and Dharok's) is slightly superior defensive stats , and is around 650k so it's worth it.
Your current setup is great however I'd suggest something that won't degrade. Dragon Platelegs are compatible with Fighter Torso, for example. Dragon Platelegs aren't that buy Runescape gold expensive and that Fighter Torso only costs a couple of hours to get. Or Bandos armour if you're a very wealthy player.