In WoW Hardcore, Rogues are a great choice for new and experienced players and offer a unique and thrilling gameplay experience. They are masters of stealth, deadly assassins, and specialists in surprise attacks and bring more crowd control (CC) to the table than practically some other class in Vanilla, equaled exclusively by Mage.
Playing a Rogue in Hardcore mode offers a unique set of challenges and some unique advantages, such as the ability to avoid unnecessary combat and choose your battles carefully. These tips are for you if you want to level up fast as a Rogue in Classic hardcore mode.
Choose the Right Race
Choose a race that suits your playstyle and preferences.
For Alliance, Human is the best choice for PvE due to their sword and mace specialization, while Gnome is the best choice for PvP due to their escape artist ability.
For Horde, Orc is the best choice for both PvE and PvP due to their blood fury and hardiness abilities, while Undead is the best choice for PvP due to their will of the forsaken and cannibalize abilities.
Do Quests Efficiently
Focus on completing quests that offer good experience rewards and are in close proximity to each other. This minimizes travel time and maximizes your leveling speed.
Grind Spots
Identify efficient grinding spots where you can kill mobs quickly and efficiently. Look for areas with high mob density and respawn rates.
Use Stealth Wisely
Take advantage of your Rogue's stealth ability to avoid unnecessary fights and skip mobs that are too hard or too far away.
Use sap, blind, kick, gouge, dismantle, and vanish to control your enemies and escape from danger. Use tricks of the trade to help your group members and reduce your threat. This saves time and minimizes downtime.
Upgrade Your Weapons Regularly
Upgrade your weapons regularly. High-damage weapons with beneficial stats, such as Agility and Attack Power, will significantly increase your leveling speed. You can also use the Auction House or professions to get better gear, but be careful not to spend too much WoW Classic hardcore gold or time on them.
Utilize Crowd Control
Make use of your Rogue's crowd control abilities, like Sap and Kidney Shot, to control multiple enemies effectively. This allows you to take on tougher mobs or complete quests involving multiple targets.
Use Combat Talent Specialization
For leveling, combat is generally the most efficient talent specialization due to its high damage output and survivability.
Use a combat 
sword specialization for leveling, as it offers the most practical and consistent damage output and better weapon progression.
Level Appropriate Zones
Level in zones that are suitable for your level and faction to ensure optimal experience gain. Avoid zones that are too crowded or too congested. You can also use an addon like Rested XP to get in-game directions for leveling. Check leveling guides to determine the best zones for your level.
Group up
Team up with other players for challenging quests or elite mob kills. Having a group can expedite the process and make certain tasks more manageable.
Use Consumables and Buffs
Use consumables such as food, 
potions, and buffs to enhance your combat capabilities and survivability. They can make a significant difference in difficult encounters.
Use Your Finishers Efficiently
Use your finishers efficiently, and don't waste your combo points on low-health targets. Use gouge and bandage to heal yourself during combat, and don't use slice and dice until rank 2 (level 42). Minimize downtime between fights by using 
First Aid for self-healing and eating/drinking to regenerate health and mana efficiently.
Use sinister strike only after your main hand strike animation to avoid resetting your swing timer due to sword specialization.
I hope these tips help you level up your Rogue in WoW hardcore mode. Remember, hardcore leveling requires caution and careful play. Always be prepared for unexpected challenges and have a backup plan in case things don't go as planned. The leveling process has always been long and difficult, especially in hardcore. You have the risk of losing your character forever, but if you choose MMOGAH, you are safe with our WoW Hardcore power leveling service!