I won't mention any names as some servers don't like when people do that, but I am a former lead balance/content developer from a successful, highly rated 3.3.5 funserver.
One thing I have noticed is the unused heroic vs normal dungeon and 10 vs 25 man raid mechanics, including normal and heroic for both 10/25 in some raids.
There is no denying that some people really only want to solo grind while others enjoy a mix of solo, grouping, or even only grouping for content and having the same tier dungeon/raid in different difficulties could address this. Dwindling private server, and wow in general, numbers lead to almost a necessity of having the ability to do all content without needing more than 1 to 3 people.
There is also a glaring uselessness of gold from what I've seen. There are MANY easy and simple ways to make gold useful and they probably should exist in some form.
My suggestions would be :
1. It seems you are planning on going with low stats on the new realm but alternatively you could just stat crunch the current realm in a matter of minutes to hit everything from stats to mob hp/damage/resistances and end up in a nice place.
2. Utilize normal vs heroic, 10 vs 25 versions of dungeons and raids. Far too many..maybe every server with custom instances just slaps it into 10 man normal. Why? Utilize normal/10 as a solo content type dungeon and then turn heroic/25 into something meant for grouping. Increased difficulty, increased drops, maybe add some drop only "heroic" versions of items in that tier.
3. Introduce tiers to the armor set instead of just level 1-30 of X item. It's kind of boring and un-immersive. Progressing through tiers gives a goal and a sense of purpose to the grind. You could simply just change level 1-5 to tier 1 level 1-5, and level 6-10 to tier 2 level 1-5 should you want to stick with the level X items. It will also allow for use of my next idea.
4. Custom set bonuses. The server I worked for where I pitched this idea is the only one I've ever seen do it, but you can easily implement GOOD blizzard or even custom set bonuses onto armor.
5. Rather than making the HC/25 man of a dungeon or raid the same tier but more difficult, use it for a different tier so you can get out more content faster, and easier. For example, ICC raid can be used for 4 tiers, without much effort other creating the 4 item sets. ICC 10 can be tier X, ICC 25 can be tier X+1, ICC 10 heroic can be X+2 and ICC 10 can be X+3. Of course not requiring 10 or 25 people, just use those available raid zones for quicker more balanced content.
6. Something I've never seen done outside of my server I worked on, custom glyphs. Most retail glyphs are useless on fun servers. Custom glyphs can be as simple as a stat boost like, a T10 glyph could be a rare drop from a T10 boss that adds stats equal to X % the stats of a T10 item. The possibilities for using and creating custom glyphs are immense. Make them drops, make them crafted to make crafting useful, make them quests rewards..but most importantly, make them matter, give them the set bonuses of blizzard tier sets, just do something! You'll be the only server that can claim to have this.
7. Role balance. Make playing towards a healer or caster rewarding instead of falling into the generic 255 trap of just going melee. Not everyone enjoys playing warrior/dk/pally/kitty :). Casters are almost always under tuned compared to melee on funservers, usually do to haste, but simple spell scaling can fix that.
One option for this is adding defensive stats and possible spell damage % healing to spells for something such as a mage, that has no self heal and no defensive rating almost forcing them to group unless they can do godlike DPS and 1 shot everything on alot of realms, if they are even worth playing DPS wise.
I've probably got more things to add as I continue playing the server but for now, I think these are simple yet effective changes that could be done to help improve the server but for now this is just my opinion from a player and developer viewpoint.