Dragon Realm has a number of design goals, i.e. desired gameplay or thematic properties. These are, in very rough order of importance:
Put Reika's mods at the center of the pack, requiring they all be extensively used in order to progress
Things obtained via Reika's mods - resources, abilities, et cetera - are often required in order to gain access to the majority of the major content
Features from other mods that are too similar to one from Reika's mods have been disabled
Balance around exploration and discovery, rather than crafting tiers or GUI manipulation, especially for magic mods
Many things require extensive exploration to find or activate, including outside of ChromatiCraft
Exploration is tweaked to provide much more reward than in a typical environment
Imitate the "Golden Age" of Modded Minecraft, circa ~1.2.5 and Tekkit
"Classic" mods like BuildCraft, RailCraft, and Forestry are included and hold a high profile
These mods often act as "gatekeepers" to newer, often-simpler mods, requiring the player at least try their content
Some modern mods are modified so that they cannot completely supplant everything else
ProjectRed is tweaked to look and behave more like RedPower
Many behaviors and appearances from those days have been brought back, even when since removed by their parent mods or vanilla updates
Try to avoid mods being ignored or only used for a handful of features
Elongate the overall progression, mainly by eliminating "shortcuts" by which a player can rapidly reach endgame, and by setting various "progression checkpoints"
Progressions are weaved together, along two main "trunks", one magic, one tech, with side branches (eg IC2 for tech).
Reduce the utilization and value of "magic blocks" which replace complex or design-requiring systems with plug-and-play "all in one" solutions
Reduce "block spam" base/automation design, by penalizing such designs and offering greater power gain via proper tech upgrades (and more complex and well-designed infrastructure) over just building more of something
Put more value in vanilla mechanics and features, such as redstone and vanilla structures
Thematic unification of mods where appropriate, to avoid a "loose kitchen sink" feel